Physics, all hail and farewell

It started from a simple introduction….


Journal: About Me page

I was still clueless when the first journal was posted, and this simple but horrifying introduction scared the life out of me;


This was the start of a tiresome year… And oh boy I didn’t think that there’re a lot to come!




As days past by Sir Lex posted something and this is what it said.


Honestly, this was the first time that I had known about the “physics classroom” and it sure helped me a lot in making the rest of my blogs even though all I did was copy, rephrase it a little bit then paste. That was my normal routine when I make my blogs.




Then one of the best ways to take a quiz was introduced to us and it was “plickers”. This way of taking as quiz was so enjoyable that I didn’t even considered it a quiz, but I’d considered it as another lecture were, we learned more about a certain topic.





And now, the moment of judgment has come… The “Grading system” was posted along with the format of our first blog and this is what it said;







Now the highlight of our  school year came, the long awaited “Stem Exhibit” where we made booths for each of our corresponding  subjects the Sir Lex encourage us to to join the division-wide exhibit and a chance to be nominated for the award “Excellence in Science or Mathematics ” come graduation day.






Lastly, now that we’re nearly finishing this game of General Physics 1 and 2, I would like to share this wonderful poem that summarizes all the good and bad experiences I had during the duration of this game. It’s to say that there are only a few moves left until we have reached the point where we claim our rights to climbed up at that stage and claim our prize and without further ado here it is;

There are the rushing waves…
mountains of molecules,
each stupidly minding its own business…
trillions apart
…yet forming white surf in unison.

Ages on ages…
before any eyes could see…
year after year…
thunderously pounding the shore as now.
For whom, for what?
…on a dead planet
with no life to entertain.

Never at rest…
tortured by energy…
wasted prodigiously by the sun…
poured into space.
A mite makes the sea roar.

Deep in the sea,
all molecules repeat
the patterns of another
till complex new ones are formed.
They make others like themselves…
and a new dance starts.

Growing in size and complexity…
living things,
masses of atoms,
DNA, protein…
dancing a pattern ever more intricate.

Out of the cradle
onto dry land…
here it is standing…
atoms with consciousness
…matter with curiosity.

Stands at the sea…
wonders at wondering… I…
a universe of atoms…
an atom in the universe




Physics, all hail and farewell

This line will forever stay in my Senior High School life because Physics had taught me a lot of things regarding how the things, world, and universe works….

I didn’t mention the “Stem Camp” because even though it wasn’t part of the body of my blog, it surely is the most memorable part of my Senior High School life.

















Mirror Image

MIRROR.1You might already have come across this image of a cat looking in the mirror seeing a lion. Yes, there’s a message behind this image often is “What matters is how you see yourself”. And the idea is great. Now, let me tell you more about mirrors.


MIRROR.2“Mirror, mirror, on the wall, who’s the fairest of them all?” This line from one of the greatest movies we’ve ever watched which is the movie “Snow White”. But, we failed to see the worth of the “Magic Mirror” where its power is unmatched and it gives the viewer to see scenes of his/her future. And a thought always stayed in my head which is if a mirror can only form an image that has a similar size and height to the original object or it forms and image that have a different height.

MIRROR.3.jpgIn addition, when I was a kid I always played in the rain and I’ve always seen fuzzy images of myself through the puddles on the streets where I played and in my head stayed this questions which are; Are all reflections real?, Are all mirrors the same?, and Are all images the same as the object being reflected?


Here are the concepts that I’ve learned are the following:



Light as we all know, behaves in a very foreseeable demeanor. If a ray of light could be discerned approaching and reflecting off of a plane mirror, then the behavior of the light as it reflects would follow a foreseeable law. The Law behind this amazing magic of mirrors is called “The Law of Reflection.”


In the picture shown above, the ray of light going towards the mirror is the incident ray or the simple called “I.” The ray of light that that is being given by the mirror is called the reflected ray (R). The broken lines that are perpendicular to the reflecting surface is called the normal line or “N.” The normal line bisects the angle formed between the incident ray and the reflected ray forming 2 different but equal angles. The angle that is between the incident ray and normal line is called the angle of incidence or incident angle or simply labelled as thetai. On the other hand, the angle in the middle of the reflected ray and the normal line is called the angle of reflection or reflected angle or simply called as thetar. These then explains the Law of Reflection which states that “the angle of incidence will always be equal the angle of reflection. “

In addition, when a ray of light strikes a plane mirror, the light ray reflects off the mirror.Thus, reflection involves a change in direction of the light ray. The convention used to express the direction of a light ray is to indicate the angle which the light ray makes with a normal line drawn to the surface of the mirror. The angle of incidence is the angle between this normal line and the incident ray; the angle of reflection is the angle between this normal line and the reflected ray. According to the law of reflection, the angle of incidence equals the angle of reflection. These concepts are illustrated in the animation above.



The principle of the multiple reflection can be seen if an object is placed between two plane mirrors incline in an angle. When this happens, we can see multiple images due to the multiple reflection of light.

The number of images we see is dependent largely on the angle between the two mirrors. And we have observed that as we decrease the angle between the mirrors, the number of images go on increasing as shown in the picture below.

The number of image increases an decreasing the angle between two mirrors

The variation of the number of images of an object placed between two mirrors with the angle between the mirrors can be described by a simple formula; Numbeof  images360∘/anglbetweemirror1




There are several characteristics of a “Plane Mirror” which are the following:

  • Plane mirrors create “Virtual and Upright Images“.
  • For plane mirrors,  the object distance (do) is equal to the image distance (di).
  • Plane mirror images is that the dimensions of the image are the same as the dimensions of the object.

In conclusion, plane mirrors produce images with a number of distinguishable characteristics. Images formed by plane mirrors are virtual, upright, the same distance from the mirror as the object’s distance, and the same size as the object.

The Image

The image shown of a candle as viewed in a plane mirror. The image has the same dimensions as the object and is the same distance behind the mirror as the object is in front of the mirror




Image result for anatomy of concave mirror

From the image above, a concave mirror can be seen were thought of as being a slice of a sphere, then there would be a line passing through the center of the sphere and attaching to the mirror in the exact center of the mirror. This line is known as the principal axis. Along the principal axis lies C, F and A (in other book it is labelled as P or V for vertex). The C is the center of curvature, and the half of C is called the the focal point or simply labelled as “F”. The distance from the vertex to the C is called as radius of curvature and half of it is the focal length which is the distance of focal point to the vertex.



The image formed by a concave mirror can be describe easily by using mnemonics L O S T. It simply stands for the location, orientation, size and type of image formed.  We can determine this characteristics by drawing the ray diagrams of a certain type of mirror. For a concave mirror, there are 4 rays to determine the LOST of an image formed are the following:

  1. Any incident ray traveling parallel to the principal axis on the way to the mirror will pass through the focal point upon reflection.
  2. Any incident ray passing through the focal point on the way to the mirror will travel parallel to the principal axis upon reflection.
  3. Any incident ray passing through C will be reflected back to C.
  4. The incident angle of the object to the vertex is the same as the reflective angle.



The location, orientation, size and type of an image formed on a concave mirror depends on the location of the object or its distance from the vertex.


  • The Location of the Object is Beyond C


As shown above, a right-side-up object is located above the principal axis at a position beyond the center of curvature (C). The ray diagram shows that the image of this object is located as an upside-down image positioned between the center of curvature (C) and the focal point (F).

Also, it can be generalized that anytime the object is located beyond the center of curvature, the image will be located somewhere between the center of curvature and the focal point. In such cases, the image will be inverted and reduced in size (i.e., smaller than the object). Such images are called real images because they are formed by the actual convergence of reflected light rays at the image location. Real images are always formed on the same side of the mirror as the object.


  • The Location of the Object is at C


In the illustration above a right-side-up object is located above the principal axis at the center of curvature (C). The ray diagram shows that the image of this object is located as an upside-down image positioned at the center of curvature (C). In fact, it can be generalized that anytime the object is located at the center of curvature, the image will be located at the center of curvature as well.

Additionally, the image will be inverted and the same size as the object. Such images are called real images because they are formed by the actual convergence of reflected light rays at the image location. Real images are always formed on the same side of the mirror as the object.


  • The Location of the Object is Between C and Frdcmc.gif

In the animation above, a right-side-up object is located above the principal axis between the center of curvature (C) and the focal point (F). The ray diagram shows that the image of this object is located as an upside-down image positioned beyond the center of curvature (C).

In addition, it can be generalized that anytime the object is located between and F, the image will be located beyond the center of curvature as well. In such cases, the image will be inverted and larger in size than the object. Such images are called real images because they are formed by the actual convergence of reflected light rays at the image location. Real images are always formed on the same side of the mirror as the object.


  • The Location of the Object is at F


As shown on the image above, the rays formed two parallel lines. These parallel lines simple means that there is no image formed. But, according to our discussion and the application for physics illustrations and concepts it stated that the location of the object is at infinity, the size is highly enlarged, the orientation is inverted and the type is real.


  • The Location of the Object is Between F and V


In the animation above, a right-side-up object is located above the principal axis between the focal point (F) and the mirror. The ray diagram shows that the image of this object is located as a right-side up image positioned behind the mirror. In fact, it can be generalized that anytime the object is located between the focal point (F) and the mirror, the image will be located behind the mirror.

In addition, the image will be upright (not inverted) and larger in size than the object. Such images are called virtual images because they are not formed by the actual convergence of reflected light rays at the image location. Virtual images are always formed on the opposite side of the mirror as the object.



The image in the diagram below is a “virtual image“. And also light does not actually pass through the image location. It only appears to observers as though all the reflected light from each part of the object is diverging from this virtual image location.



The ray diagram for convex mirrors can be drawn by following these rules:

  • Any incident ray traveling parallel to the principal axis on the way to a convex mirror will reflect in such a manner that its extension will pass through the focal point.
  • Any incident ray traveling towards a convex mirror such that its extension passes through the focal point will reflect and travel parallel to the principal axis.

The revised rules can be stated as follows:

  • Any incident ray traveling parallel to the principal axis on the way to a convex mirror will reflect in such a manner that its extension will pass through the focal point.
  • Any incident ray traveling towards a convex mirror such that its extension passes through the focal point will reflect and travel parallel to the principal axis.



This are three different ray diagrams for objects positioned at different locations along the principal axis. The diagrams are shown below.

The diagrams above show that in each case, the image is

  • located behind the convex mirror
  • a virtual image
  • an upright image
  • reduced in size

Unlike concave mirrors, convex mirrors always creates images that share common or the same characteristics. The location of the object does not affect the characteristics of the image. As such, the characteristics of the images formed by convex mirrors are easily foreseeable.

Another characteristic of the images of objects formed by convex mirrors pertains to how a variation in object distance affects the image distance and size. The diagram below shows seven different object locations and their corresponding image locations.

Also I’d observed that as the object distance is decreased, the image distance is decreased and the image size is increased. So as an object approaches the mirror, its virtual image on the opposite side of the mirror approaches the mirror as well; and at the same time, the image is becoming larger.



While a ray diagram may help determine the approximate location, orientation, size, and type of the image, it will not provide quantitative data about image distance and object size. To obtain this type of information, we can use the Mirror Equation and the Magnification Equation.

The Mirror Equation expresses the quantitative relationship of the object distance (do), the image distance (di), and the focal length (f). The equation can be written as:

On the other hand, the Magnification Equation relates the ratio of the image distance and object distance to the ratio of the image height (hi) and object height (ho). The magnification equation is written as:

These two equations can be combined to yield information about the image distance and image height if the object distance, object height, and focal length are known.



P l a n e  M i r r o r s

Some applications and uses of mirrors are listed below:

  • Periscopes and kaleidoscopes

While making periscopes which are used in submarines and kaleidoscopes which are loved by children, these mirrors are used. In submarines, the mirrors used in periscopes reflects the images of any ships present on the surface of the sea. While, mirrors used in kaleidoscopes along with color glass reflects many colorful patterns.

  • Automobiles

Vehicles use mirrors in their head lights for reflecting powerful parallel beams of light. Even we can see major uses of convex mirrors in automobiles as rear view mirrors because they give erect image and due to its curve outwards, it gives a wider field of view.

  • Torch Lights

It is used in torchlight and flashlights to reflect light beams and even used in overhead projectors for the same reason. These uses of plane mirrors in torchlight indeed can be used for searching purpose at night and dark places.

  • Shaving Mirrors

We wake up every morning and the first thing we use is the mirror to see, to shave, to brush, to do makeup etc. Without it, it would be very difficult to do these activities. Even there are uses of concave mirror as shaving mirrors in order to see larger image of face.

  • In Dentist

Dentist use mirrors while performing any examination to see images of teeth. It is also used in microscopes for reflecting the image of the object which is monitored.

  • Solar Cooker

In a solar cooker, a plane mirror reflects most of the sunlight which falls on it. Solar cooker is the most efficient way of using renewable energy for cooking purpose.

  • Security

Mirrors are used while looking for explosives underneath a vehicle. Even these mirrors are used in shops to keep an eye on the customers. Mirrors are also used in blind turns of busy roads to see the vehicles coming from other side.


C o n c a v e  M i r r o r s

Some concave mirror uses are listed in the points below.

  • Shaving mirrors

Concave mirrors are most commonly used in shaving because of its reflective and curved surface. During shaving, the concave mirror forms an enlarged and erect image of the face when the mirror is held closer to the face.

  • Head mirrors

Concave mirrors are also used by E.N.T. specialist. They put the concave mirror on their patient’s forehead. When the light rays from the light source is reflected from the concave mirror, it is focused into the ear, nose, or throat of the patient making the infected parts more visible.

  • Ophthalmoscope

Ophthalmoscope consists of a concave mirror with a hole in the center. The doctor focuses through the small hole from behind the concave mirror while a light beam is directed into the pupil of the patient’s eye. This makes the retina visible and makes it easy for doctors to check

  • Astronomical telescopes

Concave mirrors are also used in making astronomical telescopes. In an astronomical telescope, a concave mirror of a diameter of 5 meters or more is used as the objective.

  • Headlights

Concave mirrors are widely used in headlights of automobiles and motor vehicles, torch lights, railway engines, etc. as reflectors. The light source is placed at the focus of the mirror, so after reflecting the light rays travel over a huge distance as parallel light beams of high intensity.

  • Solar furnaces

Large concave mirrors are used to focus sunlight to produce heat in the solar furnace. They are also used in solar ovens to collect a large amount of solar energy in the focus of the concave mirror for heating, cooking, melting metals, etc.


C o n v e x  M i r r o r s

Some convex mirror uses are listed in the points below.

  • Inside buildings

Large offices, stores, and hospitals use convex mirror to let people see around the corner so that they can avoid running into each other and prevent any collision.

  • Sunglasses

One of the most common uses of convex mirror is for making sunglasses. The convex mirror reflects the sunlight away from the person’s eye wearing the sun glass.

  • Vehicle mirrors

Convex mirrors are widely used as rear view mirrors in automobiles and vehicles because it can diverge light beams and make virtual images.

  • Magnifying glass

Convex mirrors are widely used for making magnifying glasses. In order to make a magnifying glass, two convex mirrors are placed back to back.

  • Security purposes

Convex mirrors are also used for security purposes in various places. They are places near ATM’s so that bank customers can check if someone is behind them.


I’ve been experiencing different ways of teaching throughout the course of this subject and I can safely say that whatever way our teacher tries to do to teach us, I am able to understand and obtain all the important concepts that our teacher is giving us.

Also, I’ve been watching videos on YouTube and browsing the internet is also a great help to further understand our lessons. And lastly, discussion among classmates and friends also help our minds to brainstorm, imagine and love reflection more. And because of these, I learned to love and appreciate optics the way it should be a love and appreciated.


This is a part of the chorus of one of my most favorite songs which is “Mirror by Lil Wayne”. This lyrics sink into my head and it stayed throughout the rest of my life.

Mirror on the wall 

Here we are again

Through my rise

And fall

You’ve been my only


When I listened to this song I always remember that in the end I and I alone can be captain of my life and it showed to me that being independent isn’t bad at all and it’s actually a good thing because you can reflect on your life and to be in peace and not being disturbed by others. In addition, this song made me into the independent person I am today.




The Glue of the Universe



You don’t know what stuff is, you who hold it in you hands. Atoms? Yes, stuff is made of atoms. And every atom is a nucleus orbited by electrons. Every nucleus is built of protons. Every proton is – but there you reach the end of the line. Inside the proton lies deep, unsettling truth: Stuff is made of nothing, or almost nothing, held together by glue, lots of glue.


What I knew?

When I first heard about electromagnetism, I knew that it has something to do with the universe. Furthermore, all I had in my head was that electromagnetism is just a simple phenomenon where some magnetic force was attracting or repelling something together  and I wasn’t even sure if that was about electromagnetism. Also, I was filled with curiosity and anxiety because of how little I know about this and the feeling of not being able to grasp all the information that we will be given.

And besides, we formed new groupings and unfortunately, all of us don’t have enough knowledge regarding electromagnetism. Yes, we all had prior knowledge of it but I knew from their reactions that we did not learn it by heart and had forgotten all about the basic concepts. Despite all those negative thoughts that were running through my head.


What I learned?

After all of the activities that we had performed and also with some discussions, my initial thoughts came crashing in to form a sort of a puzzle and everything started to make sense.

  • Magnetism

In simple words, it is a force that can attract (unlike poles) or repel (like poles) objects that have a magnetic fu-e1548330492904.jpgmaterial inside them such as iron. Amaterial having this property is called a magnet.



  • Magnetic Poles 

The poles of a magnetic are usually its two ends. When a magnet is suspended freely so that it can rotate in a horizontal plane, it will settle its poles pointing to either the North or South direction. The pole that points towards the North is the North-seeking pole and vice versa.

  • Magnetic Field and Magnetic Flux

Surrounding a magnet is a magnetic field; it is a region of space where a magnet is capable of exerting a force on a magnetic material. While magnetic flux shows the quantity or strength of magnetic lines produced by the magnet. Hans Christian Oersted discovered that a current carrying wire produces a magnetic field.

  • Right Hand Rulefu5

The direction of the magnetic field produced by a current may be determined using the following rules:

Right Hand Rule 1

For a straight wire, grasp the wire with the right hand in such a way that the thumb points to the direction of the current while the fingers curl in the direction of the magnetic field.fu2

Right Hand Rule 2

In case of loop of wire and a solenoid. The fingers of the right hand are curled in the direction of the current and the thumb points to the North pole of the field or the magnetic field.fu3


  • Electromagnetic Induction

The reverse of what Oersted had said. The process by which a changing magnetic flux which is related to magnetic field produces electric current. The current and emf produced are called induced current and induced emf, respectively.

Faraday’s law and Lenz’s law describes the electromagnetic induction. Faraday’s law states that whenever there is a change in the magnetic flux in a circuit, an induced current and induced emf is produced. On the other hand, Lenz’s law states that the induced current flows in a direction so as to oppose the change causing it, which is the change in magnetic flux, that is why the formula has a negative (-) sign in it to indicate the direction.

Combining Faraday’s law and Lenz’s law, we have the formula which shows the relationship of all the variables included:FU4.png


How I learned?

There were many ways on how our teacher taught us about electromagnetism. From classroom discussions, where we learned about the basic concepts such as those that I have mentioned above to performing an experiment (Faraday’s and Lenz’s law). But first, before actually tackling more about the topic, we just stared at the materials for quite some time not knowing what to do which for me, is good.

Not only it awakened my curiosity of it but it is like trying to remake what the founders of the concepts did because being able to perform and prove a concept without that much knowledge is a big accomplishment and surely will boost someone’s confidence and self-esteem. And so, were given the following materials: copper wire, bar magnet, alligator clip, and galvanometer and made a couple of set ups for the experiment.

But before the activities, each group was assigned to a variable to focus on. After a lot of experimentation, researching and headaches, the next thing we did was to share our findings to the other groups. And I believe that this is an effective way to see if a student was able to understand their findings and the findings of the other groups and if he/she is able to share it to his/her group mates clearly without fail.

FF.jpgThe whole process itself may be very complex and a lot of work but in this way, students  will try and learn the topic with minimal guidance from their teacher which is again, a huge responsibility but has a great reward; the feeling of satisfaction and being proud of your achievement. 




Dilemmas. I have been in many situations like these before and I can safely say that there’s always a way of solving a problem no matter how big or small it may be and that there is more than one way of solving a problem. Yes, I wasn’t able to perform the way they did, however, I have my friends and my teachers whom I could ask for guidance; and that is my one way of solving a problem.

There are different individuals that surrounding me and each of them have different strengths and weaknesses. Moreover, I had this question were it’s about the poles of a magnet and it goes like this that “why do the N and S poles attract?” Because they are different with each other. The same goes for me, if I’m having a difficult time on something, I ask someone who has the capability of answering  my inquiries. In this way, not only we will experience a force of attraction but will strengthen the bond between us and will result to happy me and him/her being contented. 

The Capacity of Capacitors

Hey there everyone! Welcome back again. This is my 3rd blog and this is the continuation of past my past blog because it is connected to each other. And the lesson for today is all about Capacitors. Now sit back, relax and explore the things i knew before the class discussion, the lessons i learned, how i acquired this lesson, and lastly my reflection. Take your time and enjoy reading my blog till the end!f1.jpg

Electricity has become an important part of our lives. It is a form of energy that runs computers, appliances, and radios. It also lights our homes, schools, and office buildings. Without it, our world would be a much different place. In fact, before electricity was discovered, people mainly used fire to cook, to provide light and heat.



From the previous years. We already discussed about the different types of electrical circuits: Series and Parallel Circuit. And the things that remained in my mind about these 2 are: in Series Circuit, when there’s one light bulb not working, the rest will not work anymore. While in Parallel Circuit, if there’s one light bulb not working, the rest will still be working. Also Capacitor and Inductors are already introduced to us. Both are energy storage devices which store energy, and also serve several functions in electrical and electronic circuits. Capacitor opposes change in voltage, while Inductor opposes change in current.



What is an Electronic Circuit?

An electronic circuit is a complete course of conductors through which current can travel. Circuits provide a path for current to flow. To be a circuit, this path must start and end at the same point. In other words, a circuit must form a loop. An electronic circuit and an electrical circuit has the same definition, but electronic circuits tend to be low voltage circuits.For example, a simple circuit may include two components: a battery and a lamp. The circuit allows current to flow from the battery to the lamp, through the lamp, then back to the battery. Thus, the circuit forms a complete loop.Of course, circuits can be more complex. However, all circuits can be distilled down to three basic elements:

  • Voltage source: A voltage source causes current to flow like a battery, for instance.
  • Load: The load consumes power; it represents the actual work done by the circuit. Without the load, there’s not much point in having a circuit.
    The load can be as simple as a single light bulb. In complex circuits, the load is a combination of components, such as resistors, capacitors, transistors, and so on.
  • Conductive path: The conductive path provides a route through which current flows. This route begins at the voltage source, travels through the load, and then returns to the voltage source. This path must form a loop from the negative side of the voltage source to the positive side of the voltage source.

The following paragraphs describe a few additional interesting points to keep in mind as you ponder the nature of basic circuits:

  • When a circuit is complete and forms a loop that allows current to flow, the circuit is called a closed circuit. If any part of the circuit is disconnected or disrupted so that a loop is not formed, current cannot flow. In that case, the circuit is called an open circuit.

  • Short circuit refers to a circuit that does not have a load. For example, if the lamp is connected to the circuit but a direct connection is present between the battery’s negative terminal and its positive terminal, too.

Current flows everywhere it can. If your circuit has two pathways through which current can flow, the current doesn’t choose one over the other; it chooses both. However, not all paths are equal, so current doesn’t flow equally through all paths.For example, current will flow much more easily through the short circuit than it will through the lamp. Thus, the lamp will not glow because nearly all of the current will bypass the lamp in favor of the easier route through the short circuit. Even so, a small amount of current will flow through the lamp.

2 Types of Electrical Circuit


A series circuit has only one path for electricity to flow from one point to another. The amount of electricity in the circuit is consistent throughout any component in the circuit. When electricity flows through a series circuit, its rate of flow (speed) will never fluctuate. The total resistance of a series circuit equals the sum of individual resistances. The more resistors that a series circuit has, the more difficult it is for electrons to flow.


A parallel circuit has multiple paths for electricity to flow from one point to another. According to website All About Circuits, “all components are connected between the same set of electrically common points.” Often, resistors and sources will be connected between two sets of electrically common points. In a parallel circuit, electricity can flow in multiple directions horizontally and vertically. The components of a parallel circuit will have the same voltage across their ends and will have identical polarities.

Specialized Circuit


Properties of both series and parallel circuits can be combined to form a specialized series-parallel circuit, in which the wires or components are configured such that there are only two loops through which electricity can flow. Like series circuits, the electricity has a path to which it must adhere. Like parallel circuits, the circuit still has two sets of electrically common points.

Most Important and Basic Electronic Components

The three most important and basic electronic components are the resistor, capacitor, and inductor. They each play an important role in how an electronic circuit behaves. They also have their own standard symbols and units of measurement.


A resistor represents a given amount of resistance in a circuit. Resistance is a measure of how the flow of electric current is opposed or “resisted.” It is defined by Ohm’s law which says the resistance equals the voltage divided by the current. Resistance = voltage/current or R = V/IResistance is measured in Ohms. The Ohm is often represented by the omega symbol: Ω. The symbol for resistance is a zigzag line as shown below. The letter “R” is used in equations.


A capacitor represents the amount of capacitance in a circuit. The capacitance is the ability of a component to store an electrical charge. You can think of it as the “capacity” to store a charge. The capacitance is defined by the equation C = q/V where q is the charge in coulombs and V is the voltage.In a DC circuit, a capacitor becomes an open circuit blocking any DC current from passing the capacitor. Only AC current will pass through a capacitor. Capacitance is measured in Farads. The symbol for capacitance is two parallel lines. Sometimes one of the lines is curved as shown below. The letter “C” is used in equations.


An inductor represents the amount of inductance in a circuit. The inductance is the ability of a component to generate electromotive force due to a change in the flow of current. A simple inductor is made by looping a wire into a coil. Inductors are used in electronic circuits to reduce or oppose the change in electric current. In a DC circuit, an inductor looks like a wire. It has no affect when the current is constant. Inductance only has an effect when the current is changing as in an AC circuit. Inductance is measured in Henrys. The symbol for inductance is a series of coils as shown below. The letter “L” is used in equations.


  • The resistance of a material is the opposite or the inverse of the conductivity.
  • The Ohm is named after German physicist George Ohm.
  • The Farad is named after English physicist Michael Faraday.
  • The Henry is named after American scientist Joseph Henry.
  • Combinations of capacitors, inductors, and resistors are used to build passive filters that will only allow electronic signals of certain frequencies to pass through.

Other Basic Electronic Components

  • LED

A Light Emitting Diode (LED) is a component that can give light. We use LEDs to give a visual feedback from our circuit.


A transistor is a device that regulates current or voltage flow and acts as a switch or gate for electronic signals. Transistors consist of three layers of a semiconductor material, each capable of carrying a current.

  • Integrated Circuit

An integrated circuit, or IC, is small chip that can function as an amplifier, oscillator, timer, microprocessor, or even computer memory. An IC is a small wafer, usually made of silicon, that can hold anywhere from hundreds to millions of transistors, resistors, and capacitors.



I wouldn’t be able to share with you the learning I have known  if not because of these ways which helped me a lot to understand the topics:

  • Our parol making made me see the actual connections. And how capacitors, resistors and inductors looks like.

  • Not only the parol making but also listening to our physics teacher so that i can understand more about capacitors.
  • And lastly, taking down notes because it is pretty helpful for me so that i can have a reminder.



So this time I learned how electricity works and what materials are being used to control it  like the electronic circuit having three most important things. Why? In electronic circuit, there are the most important and basic electronic components — the capacitor, inductor and resistor in order for it to work. They each play an vital role in how an electronic circuit behaves. Just like us, we have the most important things in life which are air, water and food. We need these 3 important things in life in order for us to do all the things given to us. And each of these play an important role in our lives. We need air to breathe because the air we breathe has oxygen. We need water because every human needs water to survive. We need food because it does many jobs for our body and gives us energy in order to for us to work.




What is Electronic Circuit?


What are the Two Types of Electrical Circuit?


Physics for Kids – Resistors, Capacitors, and Inductors


Electronic Components Used in Circuits


Resistors, Capacitors, and Inductors


What is Transistor?


What is Integrated Circuit?


The Unseen Field


Coulomb’s Law

The best to start any blog (I think) is with the basics.


Sadly, not everyone will always understand it the first time. But, with perseverance they or we could understand it through.


—What I Knew—

Regarding the topic on Coulomb’s Law, I had no single clue about  it before. Though I am aware of the basics such as like charges repel and unlike charges attract, and lessons I have learned related to electroscope. Later on, I found out that knowing these greatly helped me in further understanding this.


—What I Learned—


Electric field, an electric property associated with each point in space when charge is present in any form. The magnitude and direction of the electric field are expressed by the value of E, called electric field strength or electric field intensity


Where in…

E = electric field

F = electric force

q = charge in coloumb

The dimensions of electric field are newtons/coulomb, .

We can express the electric force in terms of electric field.

Take note that…

The electric field is normalized electric force. Electric field is the force experienced by a test charge that has a value of +1.

Electric field near an isolated point charge

The electric field direction points straight away from a positive point charge, and straight at a negative point charge.





1. Two unlike charges – attraction.
2. Two like charges – repulsion.
3. A charge and an oppositely charged plate.
4. Two oppositely charged plates.



To start, what is Coulomb’s Law?

Coulomb’s Law quantifies the amount of electrostatic force that two charged object exert on each other, which causes an attraction or repulsion between them.

In other words…

The electric force between charged particles is proportional to the quantity of each of the charges and inversely proportional to the square of the distance between them.



Where in…

  • F is the force exerted between the two charges
  • q1 and q2 are the two charges
  • r is the distance between the two charges
  • coulombs formula or 9 × 10^9 N*m^2/C^2 (k) , also called Coulomb’s constant.




Two point charges are 5.0 m apart. If the charges are 0.20 C and 0.030 C, what is the force between them?




If you’re up to date with the previous blogs, you’d notice that these two formulas are quite similar:

Image result for coulomb's law newtons law

Coulomb’s Law give the electric force while Newton’s Law on Universal Gravitation gives the gravitational force.


  • Attracts
  • Inverse square law
  • Surround objects
  • Cannot be shielded
  • Incredibly weaker



  • Attracts and repels
  • Inverse square law
  • Surround objects
  • Can be shielded
  • Enormously stronger



When we have more than two charges in proximity, the forces between them get more complicated.  The forces, being vectors, just have to be added up.

In other words…

Superposition Principle = The resultant force on a charge is the vector sum of the forces exerted on it by other charges.





CL pr 2

Making a free body diagram basing on the illustration above:

Finding the direction or resultant force:



There are more complicated equations than that. If you want to learn more of it, I recommend this Youtuber/vlogger called: Step-by-Step Science


Here’s the link to his playlist about Coulomb’s Law:




—How I learned—


“A good teacher can inspire hope, ignite the imagination, and instill a love of learning.”

How I learned the most is through the teachings of our very able teacher in Physics, Mr. Lex Supnet *applause*.  He showed us how it’s done were the video clips hadn’t and he helped us master it unlike the video clips would. And so, this quote says it all, Tell me and I forget. Teach me and I remember. Involve me and I learn. So, he didn’t just tolled us what is or how it really is but he teach it to us, like a normal and loving teacher he is. He most especially involved us through the discussions and arguments about what and how he got the correct answer and solution so right.




Like the gravitational law, it exist. Like the gravitational field, it exist. But, how about you and your ex? Did it exist? Maybe it’s a no or just a big maybe but we’ve gone through several challenges through out our life were it seemed like it would never end but for the people who made that law, who didn’t slept for many days, and for those that believed it would be possible but suddenly  gave up and lost hope. For you and your ex? did you go through all of that just to keep her/him? Or maybe you just gave up like the rest are and just left without a word, it hurts right?! Not to be noticed, not to be talked to, and just being ignored like an old theory that has been left but unfortunately for you the old theory will be remembered, will be praised again, and most especially it would be valued again. How about you? Do you think your past relations would be remembered, praised, and valued once more? I think not because people today, people like you, us are just not worth it to be remembered, to praised, and to be valued once more.



What’s the Charge!

Static Electricity. Have you ever rubbed a balloon on your hair? Well I did when  I was still a child I always play with my cousin’s hair that I would rubbed a comb or a balloon on it until It felt  like its heating up then  from it and I would go get some paper stripes and watch as the paper magically attract to the piece of rubber/plastic, And I’d  remember that their hair  is standing straight on end, almost seeking out the balloon. Why did this happen? I’ll tell you down below what I’ve learned.

Sticky Business


-What I Knew-

Well, I knew a little about static electricity but not so much with the device that measured it, the “electroscope” which this is all about. But I know that the balloon/comb magic I did when I was still a child was a simple device that is mostly similar to that of an electroscope. And in my early high school years I also learned about how the electric charges flow from one object to another. What I didn’t know was how to replicate the same thing I did when I was a child now.

I wanna try it too..


-What I Learned-

After doing the activity and thoroughly discussing all about behind the electroscope that I have learned on the following:


Kinds of Charging an Electroscope


  • Charging an Electroscope by Induction Using a Negatively Charged Balloon

– An electroscope is a common demonstration apparatus used by physics teachers to illustrate electrostatic principles of charging and charge interactions.

– The electroscope is most commonly used as a charge-detecting device.

– The electroscope shown in the animation below consists of a plate (near the top),a5.gif a support stand (which connects to the plate and extends through the center of the scope), and a needle which rests upon the support stand and is free to rotate about its pivot.

– The plate, support stand, and needle are all made of a conducting material which allows for both the free flow of electrons and the distribution of any excess charge throughout the electroscope.

– By observing any deflection of the needle, the presence of charge in either the electroscope or a nearby object can be determined.


  • Charging by contact

– Rub an insulator to charge it up.

– Then stroke it across the top plate of the electroscope. This will transfer charge from the insulator to the electroscope.

– This method is direct and clear to students. However, the charge left on the electroscope will not always leave it fully deflected.


  • Charging by induction

– This is a quick way to get a larger charge onto the electroscope. However, it can look a bit magical to students. So it should be used with some care.


  • Charging with an EHT or Van de Graaff generator

– You can use a flying lead connected to one of these high voltage sources to charge up the gold leaf electroscope.

– This is quick, effective and obvious to students. The other terminal of the supply should be earthed. Connect the flying lead to the supply through a safety resistor.

  • Induction Process of Charging

– Is one of the common demonstration performed with the electroscope involving this.

– A charged object is brought near to but not touching the electroscope.

– The presence of the charged object above the plate of the electroscope, induces electrons within the electroscope to move accordingly. With the charged object still held above the plate, the electroscope is touched.

– At this point electrons will flow between the electroscope and the ground, giving the electroscope an overall charge.

– When the charged object is pulled away, the needle of the electroscope deflects, thus indicating an overall charge on the electroscope.

– The process of charging an electroscope by induction using a negatively charged balloon is depicted in the animation above.


Like Charges Repel Principle


– The negatively charged balloon repels the negatively charged electrons, thus forcing them to move downwards.

– Once the electrons leave the plate and enter the needle, both plate and support/needle acquire an imbalance of charge.

– The plate acquires an excess of positive charge (since electrons have left this once neutral region) and the support/needle acquires an excess of negative charge (since electrons have entered this once neutral region).

– Once charge within the electroscope has been polarized (i.e., separated into opposite types), the bottom of the electroscope is touched by a finger.

– Being repelled by the negatively charged balloon, electrons from the electroscope exit and enter into the ground.

– Once more, this process is driven by the principle that like charges repel.


Grounding a Negatively Charged Electroscope


– The needle, being free to rotate about its pivot, will be deflected whenever the charge in the needle is the same as the charge in the upright support upon which it balances.

– Since the electroscope plate, support, and needle are connected and made of a conducting material, any charge upon the electroscope will be distributed about the entire conductor.

– Thus, if an electroscope acquires an overall negative charge, this negative charge willd1.gif be spread about the entire electroscope – plate, support and needle.

– Since like charges repel, the negatively charged support and the negatively charged needle will repel each other, causing a deflection of the needle.

– When the negatively charged electroscope is touched, its charge becomes grounded (or neutralized). This is depicted in the animation.

– The grounding process involves a transfer of electrons between the charged electroscope and the conducting object to which it is touched. When a negatively charged electroscope is touched, electrons leave the electroscope to the ground. Since electrons repel other electrons, their tendency is to spread out as far as possible through any conductor.

– To excess electrons, the farther away that they can be from one another, the better. When touched by a larger conducting material (in this case, a person), the electrons have an opportunity to spread out even further by using the vast space of the ground.

– The excess electrons leave the electroscope, thus neutralizing its overall charge. As the electroscope loses its charge, the needle relaxes back to its naturally upright position.


Two Types of Electroscope


  • Pith-ball electroscope or  straw blade electroscopes

– Consists of one or two small balls of a lightweight non-conductive substance, a spongy plant material called pith, suspended by linen threads.

– The pith ball can be charged by touching it to a charged object, so some of the charges on the surface of the charged object move to the surface of the ball.

– Then the ball can be used to distinguish the polarity of charge on other objects because it will be repelled by objects charged with the same polarity or sign it has, but attracted to charges of the opposite polarity.


  • Gold-leaf electroscope

– It consists of a vertical metal rod, usually brass, from the end of which hang two parallel strips of thin flexible gold leaf.

– A disk or ball terminal is attached to the top of the rod, where the charge to be tested is applied. To protect the gold leaves from drafts of air they are enclosed in a glass bottle, usually open at the bottom and mounted over a conductive base.


-How I Learned-

Different ways have different impacts. But as long as students are able to understand the lesson, it is effective. And I can say that everything was effective for me.

On the activity that we did. Were we made an electroscope. Honestly, at first It didn’t worked cause I didn’t removed the insulator or the coating of the copper so after removing it or scraping it the it  finally worked but when it came to charging up the electroscope,a7.jpg it took a lot more energy than to make the electroscope but when it is done charging the results were astonishing and it felt great that it worked so well.

The activity worked so well for all of us and we learned a whole lot by doing it first hand rather than just words and pictures that are shown to us.

And another thing is that the  videos I’ve watched and concepts I’ve browsed it also helped a lot in my understanding of how an electroscope really works.



There are a lot of things in life that will come unexpectedly. But we can’t do anything about it but to accept and hope for the best. As a student, there have been a lot of things that had happened and we don’t even know how did these things happened. From the unknown forces that govern our universe and to the powers that lie on the smallest things.

This blog is a crime, why? it’s because it isn’t fair for all of us. Though we’re facing it like adults in which we’re forced to do it against our will. We lost and that’s OK but bragging about it in front of our faces is just plain rude. So thanks for this hardship or should I say lecture, a lecture to always keep your head held up high no matter what challenges face your way.





Go with the Waves

All about waves

Waves are everywhere from the smallest chirp of a bird to the roaring sound of a rocket taking off. But what makes a wave a wave? What properties, characteristics or behaviors are shared by all the phenomenon which we typically characterize as being a wave? How can waves be described in a manner that allows us to understand their basic nature and qualities? So a wave can be basically described as a disturbance that transports energy but not matter; and travels through a medium from one location to another location.


First of all, a wave has different parts, namely:

  • Amplitude (A). The maximum displacement or distance moved by a point on a vibrating body or wave measured from its equilibrium position. It is equal to one-half the length of the vibration path.
  • Crest. It is the point on a wave with the maximum value of upward displacement within a cycle.
  • Trough. It is the opposite of a crest, so the minimum or lowest point in a cycle.
  • Wavelength (λ). It can be defined as the distance between two successive crests or troughs of a wave.

1239513_orig (1).jpg

Additionally the characteristics of waves are are the following:

  • Frequency (f). The number of cycles of a repeating sequence of events in a unit interval of time. The SI unit of frequency is Hertz (Hz = 1/s = s−1).
  • Period (T). The time between successive cycles of a repeating sequence of events. The SI unit of period is the second (s).
  • Wave Speed (v). Waves propagate with a finite speed and is related to wavelength, and frequency which is given by the formula v = λf.
    *Note that frequency and period are inversely proportional with each other, and
    *Frequency and wavelength have also an inverse relationship.

Second one is the types of waves according to the presence of mediums:

  • Mechanical Waves. These waves need a medium to propagate; matter is a medium (e.g. Water waves).
  • Electromagnetic Waves. These waves can travel even through a vacuum, in other words, they don’t need a medium to propagate. Seen in the image below are the different electromagnetic waves in increasing frequency.

em_spectrum_compare_level1_lg (2).jpg

Next is the classifying waves by orientation:

  • Transverse Waves. Have a perpendicular displacement of medium to the direction of travel of the wave (e.g. Transverse waves include ocean wave or when a rope is moved up and down and all electromagnetic waves are transverse waves).
  • Longitudinal Waves. Follow a parallel pattern wherein the particles of the medium have a back and forth motion along the same direction as the travel of the wave.



  • Standing Wave. Are the superposition of two harmonic waves with equal amplitude, frequency and wavelengths but moving in opposite direction. Standing wave has particular points. The node where which there is no movement at all and the antinode which is midway between the nodes and located at the greatest amplitude.

stand (1).gif

So waves can truly be everywhere. There are lots of waves all around us in everyday life, from Sound waves which is a type of wave that moves through matter and then vibrates our eardrums so we can hear. Light waves where it is a special kind of wave that is made up of photons. You can drop a rock into a well and see waves form in the water. We even use waves (microwaves) to cook our food really fast. There are a lot of things we commonly do and don’t even realize what’s behind those that we do in life. So get out there and explore and see the beauty of life.. and waves at a time.

The closer you get, the harder it seems to catch up to you..




    Let me just say that this lessons got me curious on how objects rotate and what factors are in play when it before and during and after it rotates. So i had a couple of misconception and so what every one always start with their misconceptions and i know that you too started here to. So welcome to my flight of discovery, here’s were i call the “E-N-T-R-Y phase” were our plane will start to rotate, yeah rotate. I’ll give you a little bit of clue, we learn from experience, right? So what’s better than hopping on my imaginary plane and we’ll experience together. So come aboard, here are the flight checks which are the following:

  • Is that every object has the axis of rotation were they rotate the same way all the time.
  • That weight, size, length of the object matters on how fast it will turn
  • That there is a balanced force as the object is not changing speed… but crucially it is changing velocity.




          So were now at the mid point of our flight. This is what i call the “I-N-C-I-P-I-E-N-T phase‘ were here i’ll show and tell you what i have learned so here are the following:



 Is the name of the given to rotational inertia, the rotational analog of mass for linear motion. It appears in the relationships for the dynamics of rotational motion. 


     The moment of inertia must be specified with respect to a chosen axis of rotation. For a point mass the moment of inertia is just the mass times the square of perpendicular distance to the rotation axis, I = mr2. That point mass relationship becomes the basis for all other moments of inertia since any object can be built up from a collection of point masses. Here are the concepts of moment of inertia.

Figure. 2

Common Moments of Inertia

So here lies the common moments of inertia were cylinders and spheres are used and here it is.

mic (1)
Figure. 3

     So moment of inertia in general general form is that since the moment of inertia of an ordinary object involves a continuous distribution of mass at a continually varying distance from any rotation axis, the calculation of moments of inertia generally involves calculus, the discipline of mathematics which can handle such continuous variables. Since the moment of inertia of a point mass is defined by

Figure. 4

     Then the moment of inertia contribution by an infinitesimal mass element dm has the same form. This kind of mass element is called a differential element of mass and its moment of inertia is given by

Figure. 5

Moment of Inertia: Cylinder

          The expression for the moment of inertia of a solid cylinder can be built up from the moment of inertia of thin cylindrical shells.

icyl2b (1)
Figure. 6

Using the general definition for moment of inertia:
The mass element can be expressed in terms of an infinitesimal radial thickness dr by




Substituting gives a polynomial form integral:




     A solid cylinder of mass m= 2 kg and radius R = 1 cm
will have a moment of inertia about its central axis:

icyl (1)
Figure. 7

Icentral axis = 0.0001 kg m2

For a cylinder of
length L = 2 m, the moments of inertia of a cylinder about other axes are shown.

Icentral diameter = 0.66671666 kg m2

Iend diameter = 2.66671666 kg m2

The moments of inertia for the limiting geometries with this mass are:

Ithin disk diameter = 0.00005 kg m2

Ithin rod end = 2.88888888 kg m2



Moment of Inertia: Hollow Cylinder

Figure. 8

          So the expression for the moment of inertia of a hollow cylinder or hoop of finite thickness is obtained by the same process aicyl3bs that for a solid cylinder

Some of the process involves adding up the moments of infinitesimally thin cylindrical shells. So this is the only difference from the solid cylinder is that the integration takes place from the inner radius a to the outer radius b: icyl3b

Moment of Inertia: Hoop


          The moment of inertia of a hoop or thin hollow cylinder of negligible thickness about its central axis is a straightforward extension of the moment of inertia of a point mass since all of the mass is at the same distance R from the central axis.

     For mass M = 2 kg and radius R = 1 cm
the moment of inertia is I = 0.0002 kg m2
For a thin hoop about a diameter in the plane of the hoop, the application of the perpendicular axis theorem gives I(thin hoop about diameter) = 0,0001 kg m2



     Thick Hoops and Hollow Cylinders

          ihoop2So here’s another moment inertia for a hollow cylinder For mass M = 2 kg,
internal radius a = 1 cm and external radius b = 2 cm, the moment of inertia I = 0.0005 kg m2. This may be compared with a solid cylinder of equal mass where I(solid) = 0.0004 kg m2, or with a thin hoop or thin-walled cylinder where I(thin) = 0.0008 kg m2.  The moment of inertia of a hollow circular cylinder of any length is given by the expression shown.


Moment of Inertia: Sphere

          So in the expression for the moment of inertia of a sphere can be developed by summing the moments of infinitesimally thin disks about the z axis. The moment of inertia of a thin disk is..sph3


         So here’s the moment of inertia of a sphere about its central axis and a thin spherical shell are shown.

For mass M = 2 kg
and radius R = 1cm
the moment of inertia of a solid sphere is
I(solid sphere) = 0.00008 kg m2
and the moment of inertia of a thin spherical shell is
I(pherical shell) = 0.0001333333 kg m2



Moment of Inertia: Rod

          Calculating the moment of inertia of a rod about its center of mass is a good example of the need for calculus to deal with the properties of continuous mass distributions. 

     The moment of inertia of a point mass is given by I = mr2, but the rod would have to be considered to be an infinite number of point masses, and each must be multiplied by the square of its distance from the axis. The resulting infinite sum is called an integral. 

The general form for the moment of inertia is:rod3

     When the mass element dm is expressed in terms of a length element dr along the rod and the sum taken over the entire length, the integral takes the form:rod4

For a uniform rod with negligible thickness, the moment of inertia about its center of mass is

For mass M = 2 kg and length 
L = 1 m, the moment of inertia is 
I = 0.16666666 kg m²

The moment of inertia about the end of the rod can be calculated directly or obtained from the center of mass expression by use of the Parallel axis theorem.

The moment of inertia about the end of the rod is

I = 0.66666666 kg m².

If the thickness is not negligible, then the expression for I of a cylinder about its end can be used.


Rotational Analogs

To Force

Fullscreen capture 632016 41005 PM.bmp (1).jpg          Consider a force F exerted tangentially on the rim of a wheel or disk. The rim is at a distance r from the axis of rotation. We can formally define torque, represented by the Greek letter  τ, in terms of the force F and the distance r: τ=rF=rFtangential

     Where r is sometimes referred to as the moment arm of this applied force—the further away from the axis a particular force is applied, the more torque is exerted, producing more change in rotational motion. Torque can be thought of as the “turning effectiveness of a force” or “rotational force.” Fullscreen_capture_632016_41833_PM.bmp

 What happens if the applied force is not purely tangential, as in the second circle in figure? This force can be broken down into its tangential and radial components,  Ftangential and FradialFradial . Note that the radial component FradialFradial of this force has no effect on the rotational motion of this disk! So, for any general force exerted a distance r from a rotation axis, it is only the tangential component of this force (Ftangential)(Ftangential) that will affect rotational motion.

     The tangential component of the force can always be found with the appropriate trig function. If θθ is the angle between the applied force, F, and r, the tangential component is FsinθFsin⁡θ .

     Torque, along with other angular variables, has vector properties. If we imagine the torque causing the object to rotate about an axis perpendicular to the plane defined by the force and the moment arm, r, we can use the same right-hand-rule introduced for finding the direction of θθ and ωω to find the direction of the torque ττ . If you curl the fingers of your right hand in the direction of rotation that the torque would cause, then your thumb points in the direction of the torque.


To Momentum

          It is useful to consider the angular momentum of both a point object as well as the angular momentum of extended objects. In either case, we need to be clear about the axis (or point) about which we are calculating the angular momentum

     A particle with momentum p, located at position r from some point in space has angular momentum L about that point with a magnitude given by L=rp=rptangential


     Note that the angular momentum is related to the linear momentum the same way as torque is related to force. Both L and  τ depend on the choice of the point in space to which they are referenced. Like torque, angular momentum is a vector. Its direction is perpendicular to both r and p and is given by the RHR.

     If a system has many parts, its total angular momentum is the vector sum of the angular momenta of all the parts: L=L1+L2+L3=Li

     A rigid object with rotational inertia I about some particular axis has an angular momentum about the same axis given by L=Iω

The direction of  L  is parallel to the direction of ωω. These directions are shown in the figure.Fullscreen capture 632016 42931 PM.bmp.jpg


To Mass

   Recall that for transnational motion an object with a large amount of inertia has a greater momentum than an object with a small amount of inertia, both moving at the same speed. Mass, m, is the measure of inertia in transnational motion.

     The rotational motion analogy to inertia is rotational inertia (or rotational mass), or in very technical language, moment of inertia. With a given net torque,  Στdifferent objects will experience different rotational accelerations.

     The rotational inertia of an object does not depend solely on the amount of mass in the object, but on how this mass is distributed about the axis of rotation.

     For the simplest case of a point mass m moving in a circle of radius r, its rotational inertia is given by: I=mr2

     This definition allows us to calculate the rotational inertia of any object, provided we know the position r of every portion of its mass as measured perpendicularly with respect to the axis of rotation: I=m1r21+m2r22+m3r23+=mir2i

     This looks a lot like calculus (which it is in the limit of infinitesimally small mass increments.) The table below gives the rotational inertia of several simple geometric shapes, as calculated in the limit of infinitesimal increments of mass using this equation.

Object Rotational Inertia Illustration 
Point mass m moving in radius r I=mr2
Thin ring of mass m, radius r rotating about center I=mr2
Thin rod of mass m, length L rotating about one end perpendicular to the rod I= 1/3mL2
Thin rod of mass m, length L rotating about one e perpendicular to the rod I= 1/12mL2
Disk of mass s, radius r, rotating about an axis perpendicular to disk though the center I= 1/2mr2
Sphere of mass m, radius r, rotating about an axis thorough the center I= 2/5mr2
Thin hollow spherical shell of mass m, radius r, about an axis through the center I=2/3mr2

     As seen from the formulas in the table, objects with the same mass can have very different rotational inertia’s, depending on how the mass is distributed with respect to the axis of rotation.

     Also, it is possible for an object to change its rotational inertia (e.g., a gymnast tucking in or extending arms and legs), which can lead to dramatic results as net torques are applied. The rotational inertia of a composite object is the sum of the rotational inertia’s of each component, all calculated about the same axis.


     So for a ring and a disk stacked upon each other and rotating about the symmetry axis of both, the rotational inertia is :


The SI units of rotational inertia are  kg⋅m2


To Impulse

          The angular analog to impulse, is angular impulse


or, if the torque is constant with time, or we define an average torque τavg



          This is where I tell you know how I learned those things were we are here now on the “D-E-V-E-L-O-P-E-D phase” so here are the following factors that helped me in further understanding this topics:



          So an object hanged on a rope L=0,5m, does rotational motion. If the angle between rope and vertical is 370, find the tangential velocity of the object. (g=10m/s2, cos370=0,8, sin370=0,6)
     Here’s the free body diagram of system is given below;
     And here’s the horizontal component of tension on the rope makes object rotate.
 TX=mV2/r, TY=m.g
Radius of the motion path is;
     And here’s another problem with the solution.
     An object having mass m does rotational motion. Its angular velocity is ω and radius of motion path is r. Find kinetic energy of the object in terms of r, ω, and m.


So we did a game were we rolled objects down an inclined plane or a ramp so here are the awesome pictures that I have taken and hopefully you’ll spot the hilarious faces made by my classmates.


  This were I learned the most ’cause the one that is teaching looks like a freaking scientist from movies and so I listened to it closely. Here’s the title,

Walter Lewin demonstrates moment of inertia”




          This is the end of our flight hope you enjoyed it! Now imagine this, like the video about the old guy and the ramp and a couple of cylinders and you’re that cylinder. Now the ramp serves as our life and  at the top of it that the point were we are born and at the bottom is our end. So you’re cylinder that’s hollow inside, that’s longing for something in life that will you whole. Now you started rotating, you encountered a couple of bumps, and ditches so what that didn’t stop you from finishing your requirements. You know inside of you that you’re weak ’cause your not whole yet and get jealous of others ho found their something that made them whole and you know what they died first, yes! they got buried first. So don’t neglect your self for being a hollow cylinder ’cause your unique from everybody else and that you live your life a day at a time and no matter how slow you rotate you know deep inside of you that you can reach that something that will make you whole. And i would like to share a meme that i made 🙂 .


And if you’re wondering why the weird “PHASES’ I got them from the phases of a plane that will spin.




Lesson 2 – Projectile Motion “A RAINBOW OF NUMBERS”



WOW!… M-A-G-I-C!



“What I know”

          The concept that i know was that the only force acting upon upward moving projectile is gravity . So my conception of motion is that an object is moving in an upward motion, then there must be an upward force. And if that object where to move upward and rightward, then there must be bot an upward and rightward force.

          The misconceptions that i found out were that of a force is in the direction of motion, and an acceleration is a displacement. 



“What I learned”



  • So a projectile is an object upon which the only force acting is gravity.motio.8 For example, if an object which is thrown upward at an angle to the horizontal is also a projectile if provided that the influence of air resistance is negligible.


  • A projectile has a single force that acts upon it – the force of gravity. If there were any other force acting upon an object, then that object would not be a projectile.u3l2a3 Thus, the free-body diagram (Fgrav)  of a projectile would show a single force acting downwards and labeled force of gravity.





Projectile Motion and Inertia

  • So according to Newton’s first law of motion, such a cannonball would continue in motion in a straight line at constant speed.u3l2a4 If not acted upon by an unbalanced force, “an object in motion will …”. This is Newton’s law of inertia.


  • So now suppose that the gravity switch is turned on and that the cannonball is projected horizontally from the top of the same cliff. What effect will gravity have upon the motion of the cannonball? u3l2a6
  • u3l2a5Because Gravity is the downward force upon a projectile that influences its vertical motion and causes the parabolic trajectory that is characteristic of projectiles.




Horizontally Launched Projectiles

  • So let me tell you what I’ve learned so far, so let us consider the example before of  a cannonball projected horizontally by a cannon from the top of a very high cliff. In the absence of gravity, the cannonball would continue its horizontal motion at a constant velocity.  This due to law of inertia.u3l2b2 And furthermore, if merely dropped from rest in the presence of gravity, the cannonball would accelerate downward, gaining speed at a rate of 9.8 m/s^2 every second. This is consistent with our conception of free-falling objects accelerating at a rate known as the acceleration of gravity.


  • And our thought experiment continues and we project the cannonball horizontally in the presence of gravity, then the cannonball would maintain the same horizontal motion as before – a constant horizontal velocity.u3l2b3 Henceforth, the force of gravity will act upon the cannonball to cause the same vertical motion as before – a downward acceleration. The cannonball falls the same amount of distance as it did when it was merely dropped from rest.


  • To summarize it all i devised a table to further understand horizontally launched projectiles. 
    HorizontalMotion VerticalMotion
    Forces(Present? – Yes or No)(If present, what didn’t?) No YesThe force of gravity acts downward
    Acceleration(Present? – Yes or No)(If present, what didn’t?) No Yes“g” is downward at 9.8 m/s/s
    Velocity(Constant or Changing?) Constant Changing(by 9.8 m/s each second)


Non-Horizontally Launched Projectiles

  • So now let us suppose that our cannon is aimed upward and shot at an angle  horizontally from the same cliff.u3l2b5.gif In the absence of gravity supposing that the gravity switch could be turned off the projectile would again travel along a straight-line, inertial path.


  • So if the gravity switch could be turned on such that the cannonball is truly a projectile, then the object would once more free-fall below this straight-line, inertial path.u3l2b6 In fact, the projectile would travel with a parabolic trajectory.


  • So in conclusion, projectiles travel with a parabolic trajectory due to the fact that the downward force of gravity accelerates them downward from their otherwise straight-line, gravity-free trajectory. This downward force and acceleration results in a downward displacement from the position that the object would be if there were no gravity. The force of gravity does not affect the horizontal component of motion; a projectile maintains a constant horizontal velocity since there are no horizontal forces acting upon it.



“How I Learned”



The Catapult experiment  that we did was thrilling and very much educational in which we saw how the object flew with the gravity switch turned on

Look at that marshmallow fly?! WOO!!

 but how i wish that we could do the same experiment but with the gravity switch turned off.


So we observed that the object or marshmallow flew in a parabolic line in which it looked like an arc or better yet a rainbow. So we witnessed how gravity acted downwards upon the marshmallow to affect its vertical motion and caused the parabolic trajectory that is characteristic of projectiles. So I’ve learned that the best way to learn in physics is through experiments like this were you put all the knowledge that you’ve gained in class and using in real life where in this case a catapult experiment which we won actually. Thanks to Lalaine for single handedly taking on the task of making our catapult.


An amazing piece of engineering by Lalaine Cardenas






We wouldn’t have learned how a projectile moves in the air without the long-long hours we’ve spent learning how it really works and understanding the science under this amazing lesson about projectile motion. 

No. 1 … WOO! … We Won!!

And this proved to be successful because we learned, understood, and applied what we’ve gained inside of the room to the outside. Trough the calculations we’ve hardly could understand but we’ve conquered it and almost got a perfect score in the write up the we’ve made, yey!!




Through the video simulator that our physics showed and demonstrated it to us showed how the initial speed, mass, air resistance, and angle played a big rule in determining the spot were the projectile would land or hit.


Super high-tech ang pa activities ni Sir!!

Because of this video simulator we had a little bit of fun tinkering with the angle, initial speed, etc. and we found out that the angle you must fire at is 45 degree angle because it gives the most amount of distance whatever initial speed you might put or have.







          So I’ve thought of this question while i was doing this journal and it goes like this “a projectile move in a parabolic path. Which part of your life seems to move like a projectile? Why do you say so?”, yes, and my answer is my family life where i feel like i’m at the bottom sometimes were they treat me as nobody and when i’m at the top or peak they care for me, show how great i’m to them when i’m with them and show how much they love me. 

          And one more about my whole life so far, so a projectile move towards the ground because of the influence of gravity. Similarly, this tells you that there are forces that can influence your success. All you have to do is to learn to deal with these forces so that you still reached your goal.

          So just like a two-dimensional motion with horizontal and vertical components, your life also has many components or aspects. These include physical, social, emotional, and spiritual aspects. 

Now we’re at the end of the rainbow. I hope you’re satisfied with what I’ve done because i’m sure am satisfied and relieved that i got the chance to let out my emotions and into words which i could hardly tell to someone. Now you’ve witnessed the feeling of walking in a rainbow. A rainbow that is not only of colors but with numbers to. So let me end it with one more reality check which is this “Challenges are like a catapult in which it pulls you down but their will always come a time in which someone will pull the trigger and send you flying in the right path, to your goals, to your love one’s, and to your happiness.






































Introduction to Free Fall





Free Falling is thing that is falling under the sole influence of gravity. So any object falling that is being acted upon only by the force of gravity is said to be in a state of “FREE FALL”.







1. Free-falling objects do not encounter air resistance.

  • Free Fall and Air Resistance

free fall.5

So it stated that all objects (regardless of their massfree fall with the same acceleration – 9.8 m/s/s.

This particular acceleration value is so important in physics that it has its own amazing name – the acceleration of gravity– and its own amazing symbol – “g”.

Newton’s second law of motion which is (Fnet = m•a) will be applied to analyze the motion of objects that are falling under the sole influence of gravity (free fall) and under the dual influence of gravity and air resistance.

  • Free Fall Motion

As I learned, free fall is a special type of motion in which the only force acting upon an object is gravity. Objects that are said to be undergoing free fall, are not encountering a significant force of air resistance; they are falling under the sole influence of gravity. Under such conditions, all objects will fall with the same rate of acceleration, regardless of their mass. But why?

free fall.3Let’s assess the‘free-falling motion of a 1000-kg baby elephant and a 1-kg overgrown mouse’.

If Newton’s second law of motion were applied to their falling motion, and if a free-body diagram were constructed, then it would be seen that the 1000-kg baby elephant would experiences a greater force of gravity.

Because of this greater force of gravity would have a direct effect upon the elephant’s acceleration; thus, based on force alone, it might be thought that the 1000-kg baby elephant would accelerate faster.

But because of the acceleration depends upon two factors: force and mass. The 1000-kg baby elephant obviously has more mass (or inertia). This increased mass has an inverse effect upon the elephant’s acceleration. And thus, the direct effect of greater force on the 1000-kg elephant is offset by the inverse effect of the greater mass of the 1000-kg elephant; and so each object accelerates at the same rate – approximately 10 m/s/s.

Because of the ratio of force to mass (Fnet/m) is the same for the elephant and the mouse under situations involving free fall.

This ratio is sometimes called the gravitational field strength and is expressed as 9.8 N/kg (for a location upon Earth’s surface).

Because of the gravitational field strength is a property of the location within Earth’s gravitational field and not a property of the baby elephant nor the mouse. All objects placed upon Earth’s surface will experience this amount of force (9.8 N) upon every 1 kilogram of mass within the object.



2. All free-falling objects (on Earth) accelerate downwards at a rate of 9.8 m/s/s (often approximated as 10 m/s/s for back-of-the-envelope calculations)

free fall.7.gifBecause the free-falling objects are accelerating downwards at a rate of 9.8 m/s/s, a ticker tape trace or dot diagram of its motion would depict an acceleration.

The dot diagram at the right illustrates the acceleration of a free-falling object. And the position in which the object at a regular time intervals – say, every 0.1 second – is shown.

The fact that the distance that the object travels every interval of time is increasing is a sure sign that the ball is speeding up as it falls downward to the ground.I recall from the earlier lessons, that if an object travels downward and speeds up, then its acceleration is downward.




The factors that helped me in learning the lesson are the following:



The Free Fall experiment we did was thrilling and very much educating. We had the chance to witness for ourselves how gravity really works and proving Galileo’s theory to the test.37045792_1846415628986536_5528747413994471424_n

Watching the basketball fall is mesmerizing to watch. Applying what we learned in the classroom and not only confined in a room but being free to learn outside the room. 37091440_1846424415652324_9081083614334025728_n


We would’t have learn how gravity works if not for the hours of lectures in our classroom. Without the longs hours of understanding thoroughly the lesson and gaining the necessary knowledge first.  Appealing to us who learn by listening.





Free-falling objects, like all objects, are influenced by gravity, which pulls you down toward the center of Earth. In life, there are many things that can pull you down. They hinder you from reaching your goals. You should do your best to overcome the challenges.