## Tuesday, May 17, 2011

### Electricity Circuits :)

An electric circuit is the path through which electric current flows from a generator to a load. In electricity, we studied three different types of circuits, parallel, series, and series-parallel combination circuits. We used lightbulbs to demonstrate the flow of electricity through the circuits. A DC circuit is a direct current circuit which means it is a circuit that is connected to a source of power, like a battery. In the picture below is an example of a series circuit.

In this picture you can see the two lightbulbs connected in series. The lightbulbs are resistors. A series circuit is a circuit where all of the resistors are connected directly to the battery and because of Kirchhoff's first law. The current is the same throughout the entire circuit because the resistors are connected to each other and only create one path for the current to travel. It is in a circle in which the current is constantly flowing and there are no "forks in the road" or places for the current to split. The total voltage is the sum of both of the resistors' voltages. The voltage is the energy of the circuit and is distributed to the light bulbs. The voltage of each light bulb is the current (which is constant in series) times the resistance of the resistors. The total voltage of the circuit is equal to the sum of the voltages in the entire circuit. When one of the bulbs is removed, all of the lights go out because the path of the current is interrupted and the current cannot reach the other bulb.

The picture above is of a parallel circuit. ﻿Parallel circuits are circuits where each resistor has a different path by which the current can flow. The current of a parallel circuit is not constant because there is more than one parth by which the current can flow so it splits and goes to the different resistors/bulbs. The sum of the currents of each resistor is equal to the total current. The voltage of the parallel circuits is a constant value in the whole circuit. The voltage of each light bulb does not affect the voltage of the battery because equal to the battery since it is not on the same path as the battery's voltage. When a bulb is removed from this circuit, the other bulb remains lit because there is still a complete path for the current to travel.

The image above is of a series-parallel combination circuit. This circuit consists of a set of parallel resistors and the parallel set is connected in series to another resistor. In this circuit, the current is determined by finding the total resistance of the parallel section and adding that to the resistance of the resistor in series with the parallel bit. Once you get the total resistance you can find the total current. The total current changes due to the resistance. The voltage of the combination circuit is also a combination of the parallel and series. The voltage of the parallel part is equal (explanation above) and the voltage of the part in series can be found using the series explanations. The reason the bulb in series is brighter is because the total current is running through this portion unlike in the parallel portion where the current is split. When a bulb is removed from the parallel portion, the rest of the bulbs will stay lit because there is still a complete path and the current doesn’t need to go through the section of the removed bulb. When the bulb in series is removed, the entire circuit goes out because the path of the current is interrupted and there is basically a hole in the circuit so the current cannot travel.
In all three types of circuits, the current and voltage act and are distributed differently depending on the path of the wires and how the resistors are connected.

## Tuesday, May 10, 2011

### Tiny Wings Roller Coaster

Our physics class was assigned to create an amusement park. We broke up into groups of three or four and created an engineering firm name and chose which roles each of us would have in the creation of our ride. My group decided to create a roller coaster. The theme for our Amusement park was iphone apps and we chose to make a Tiny Wings Roller Coaster. We used the templates our teacher gave us to create the tracks and we made our coaster using card stock and glue to keep it together. We decorated it with gold coins and small birds to represent the app "Tiny Wings". We then tested our ride to make sure it worked and collected data in order to find the Friction of the ride and the Conservation of Energy throughout the ride. Below you will find a short Prezi explaining the physics of the ride and a link to our teams page about our roller coaster.

Our Prezi: *Note that clicking on the play button will take you to the prezi website to view it

## Thursday, April 28, 2011

### Look! It's the Sun! And another one... and another one?

Natural Category Demonstrating Reflection:

This is a picture I took on my way to school one morning of the sunrise. I looked out my window and noticed I could see the sun in both the mirror, and the side of the car. The law of reflection states that on a straight planed mirror, the angle of incidence is equal to the angle of reflection in respect to the normal. Basically this means the angle at which the, in this case, light of the sun hits the mirror, you view the image of the sun at the same angle that it hits the mirror. The normal is an imaginary line that is perpendicular to the surface of the mirror. This mirror however, is convex or diverging. This means the mirror is curved outwards and the image seems to be smaller than it actually is. That is why all car mirrors have the warning “objects in mirror are closer than the appear” which can be seen at the bottom of the mirror. Now, the reason there are three suns in this picture is very simple. The sun’s image is viewed in three spots, an image in the sky, in the window, and in the door, the image in the window and in the door are both reflected twice. Once, in the window and door, then that image is reflected again into the mirror, causing the illusion of the three suns.

## Tuesday, March 29, 2011

### The Electromagnetic Spectrum... Huh?!?!?!?

I bet that just from this title you already susupect this will be a very confusing blog about a confusing topic. Well You Are WRONG! Really the electromagnetic spectrum is just a fancy shmancy term scientists use to group together all seven types of waves. Some characteristics of electromagnetic waves are they all are a type of radiation. These radiations are a stream of photons(basic particles of electromagnetic radiation) that travel in waves and each contain an amount of energy that varies depending on which type of wave is being transferred. The seven waves that form the spectrum, in order of wavelength sizes in longest to shortest are: Radio, Microwave, Infrared, Visible, Ultraviolet, X-Rays, and Gamma Rays. All seven of these waves have very similar characteristics and together, form the Electromagnetic Spectrum. A Tagxedo of these words can be found below:

﻿
The one thing that makes these waves unique from all other types of waves is the fact that none of them require a medium to travel through, they can travel through a vacuum. Now, I will discuss in depth TWO of these seven waves. The two waves I have chosen are Gamma Rays and R﻿adio Waves.

Gamma Rays:
Gamma Rays, opposing popular opinion, (at least my opinion), DO EXIST! In fact they have the smallest waves and the most energy in their photons of any other waves in the Spectrum. Since Gamma Rays are so small, they can and will often pass through the atoms of detectors. Therefore a special kind of detector, which contains densely packed crystals, is used to detect Gamma Rays. They can detect these rays by observing the effects on the matter contained in the detector. Gamma Rays can do three things with matter: 1. they can just bounce off the electrons in the matter, 2. they can push the electron to a higher energy level, or 3. they can create new matter together. The picture below is called the Compton Scattering. It is a physics experiment that authenticates the nature of radiation waves to be particles and waves. When the Gamma ray interacts with matter, its energy decreases as the wavelength increases. It was first discovered by Arthur Holly Compton in 1923 and convinced physicists that Gamma Rays can behave as a stream of particles whose energy is proportional to the frequency or as simply a wave.
Gamma Rays have a frequency of less than
and a wavelength of greater than
Gamma Rays are used to determine which basic elements are on other planets by scientists and can be found in supernovas, nuetron stars, and pulsars in the night sky.

Radio waves are the opposite of Gamma Rays, at least in the respect of their wave lengths. Radio wavelengths are the longest wavelengths in the electromagnetic spectrum. They were discovered in the late 1880's by Heinrich Hertz. Radio waves do exist on their own in nature, they are not soley for playing music. Almost every planet produces radio waves in space. Below is a picture of a graph of the radio emissions of different planets.

Radio waves have a frequency of ﻿
and a wavelength of ﻿
﻿Usually, as the frequency of a wave gets higher, the length of the wave gets shorter. Radio waves are used every day to transmit music over the radio stations and television. The military also uses Radio waves to communicate with eachother over long distances.

Works Cited:
http://missionscience.nasa.gov/ems/01_intro.html

## Tuesday, January 25, 2011

### Energy at Six Flags!!

This unit in physics we studied Conservation Laws of Energy. We learned about how to use bar graphs as energy flow diagrams. Energy is everywhere, although the amount of energy never changes, the method in which the energy is stored changes. Energy can be stored as elastic, kinetic, gravitational, potential, and chemical potential. We defined energy transfer as work or W. We learned how to find work, power, kinetic and potential energy, and the work energy theorem.

I made a Glogster to help explain this unit more effectively:

## Sunday, January 16, 2011

### Round and Round and Round We Go!

This is what I learned about circular motion and gravity. I learned that in order for an object to be in any kind of circular motion, there needed to be some sort of centripetal force keeping the object moving in a circle. Whether the centripetal force is the friction between car tires and the road, or just the tension of a string swinging a ball, it is always there. I learned that the velocity is constantly changing when an object is in circular motion because the direction is always changing. I learned the Law of Universal Gravitation and how every object attracts every other object in the universe. I learned that the variable G is always $6.67x10^{-11}N.m^{2}/kg^{2}$. I also learned how to find the acceleration due to gravity in situations not on the earth's surface.
When we first started out this unit I had some difficulties understanding all of the concepts. I especially had trouble with figuring out which equation to use with the given information. It was very difficult for me to change equations in order to find different quantities. What I have found difficult about what I have studied is finding and using the sum of the forces equations when dealing with motion in vertical circles. I had lots of trouble figuring out how to use the sum of forces (sigma F) equations with the new equations we learned specifically for circles. The most difficult concept for me to comprehend was gravitational acceleration, specifically when we had to use ratios to find our answers. I eventually figured out how to use ratios in these cases and once I did everything became infinitely easier. What I found most simple was the whole concept of gravitational acceleration. The whole concept was easy to understand and made sense so it did not cause me much trouble.
My problem solving skills have definitely increased over the course of this unit. As usual, I started out the unit very confused and unsure how to solve most of the problems, but as I worked more problems and did the classwork in our notes, I became more confident. One of my weaknesses at the beginning was calculating the centripetal force when there is very little information given. Say you are in a car and about to enter a traffic circle with a radius of 30 m. You are traveling at 6 m/s and the mass of your car is about 300 kilograms. In order to find the centripetal force you would use the equation $F_{c}=mv^{2}/r$. Then you would plug in the information and you would get Fc=360 N. Now that seems fairly simple, but if you take away one of the variables and everything becomes much more complicated. I think the main thing that made this unit difficult for me was that for almost every single problem there was more than one step to find the answer and I would get confused on when to do what and how. Mostly all of the gravitational problems were fairly easy to comprehend. This unit has definitely helped me to better understand circular motion, gravitational acceleration and how forces are everywhere.

## Sunday, January 2, 2011

### Mythbusters: Physics Edition

In our physics class we created our own mythbusters episode to disprove some common myths about physics.

Myth 1: An object always moves in the direction of the net force exerted on it.
When first looking at this you think, well this should be true right? Wrong! When you take a closer look here's what you get:

For this experiment we are going to focus on the time the ball is actually rolling not when it is initially pushed. So when you look at the FBD of the ball while it is in motion you will see that the net force of the ball is actually backwards even though the ball is rolling forwards.

The net force would be ΣFx = -Ff but the ball is not moving in a negative direction, it is moving in a positive direction; therefore this myth is... BUSTED!

Myth 2: An object always changes its motion if there is a force exerted on it by other objects.
Again this seems pretty reasonable, but my team of mythbusters found a way to bust this myth too.

So in this experiment, the tennis ball hit the bowling ball while it was in motion. If you look at the FBD of the bowling ball at the moment the tennis ball hits it, you see that even though there is an applied force going in the negative  direction, the ball continues its motion unchanged. Although the ball might have slightly slowed down, we could not detect a detectable amount of change in motion in the ball.

Even though there is an applied force going in the negative direction, the ball continues it's path moving in the positive direction unchanged. This myth is totally BUSTED!

Conclusion:
Neither of these two myths was too big of a challenge for our superior team of mythbusters. We couldn't prove these myths wrong completely because we lack the proper materials but based on our data (what we saw the ball do) we can loosely conclude that these myths are busted.
People believe that an object always moves in the direction of the net force exerted on it because it sounds pretty reasonable. If you push a wagon, most likely the wagon will go in the direction you pushed it, it won't randomly start going sideways or backwards. But, in some cases, the ΣF is not going in the same direction as the object. People usually believe this myth because we forget the force of friction exists, this myth would be true if friction did not exist but there is friction in our world, therefore this myth is untrue. People will also believe that an object always changes its motion if there is a force exerted on it by other objects because again, it sounds reasonable. If you push that same wagon it usually will start moving in the direction you pushed it. But if the wagon weighs 600 pounds and you only weigh 90, there is not a good chance that you will be able to get the wagon to move. So if the applied force is significantly smaller than the object then the object will not change its motion. People just don't like to think about the special cases of things, mostly they will just look at it and think hey that sounds right and not try to prove it wrong to themselves to prove themselves right. People are lazy sometimes and sometimes people just say oh that sounds right and do not bother to try it out.