Blog #13 Contact Lenses

I use contacts everyday. I am farsighted, meaning that I cannot clearly see things that are farther away. Therefore, I use diverging lenses in order to create virtual images of objects so that they appear sharper. They look smaller and are rightside up. Diverging lenses curve towards the center whereas converging lenses curve away from the center.

Guitars are phySICK

This is a picture of two guitars in my house.  Guitars can play a wide range of notes, or frequencies.  We learned that the formula for a string's frequency is: f=v/2L.  Coupled with the V=sqrt F/m/l equation, we can explain why increasing the tension increases the frequency: if force (tension) is increased, then velocity is also increased, and therefore, frequency is increased. You can also shorten the length of the string played, and decreasing the length will also result in a higher frequency.

I could apply the physics knowledge in this blog and become the next Jack Johnson.

Blog #11 Swing Resonance

http://griffinphysics.blogspot.com/2011/12/physics-swing-circular-motion-blog-5.html

This swing in this blog's video demonstrates the concept of resonance.  If I push at the right time and create a "standing wave" I can increase the amplitude of the wave.  The amplitude in this instance is the height of the swing, by pushing the swing when it is going forward, I can create resonance.  The frequency and wave speed will still remain the same. If I increased the frequency of the swing, then the wave length would decrease.

Physics Blog #10 Transformers

Today while driving home from school I realized that there was some physics above me in disguise:transformers! Transformers decrease or increase the amount of voltage by using coils. The power plant outputs a tremendous amount of voltage (it uses A/C b/c a DC would destroy the wires) and the transformers decrease the voltage so that it can run through the wires safely. There are two coils, the voltage goes down the outside one (which has the most coils) and is inducted into the other (which has less coils and therefore less voltage).

Physics Blog #9 Light Switch

This video demonstrates a light switch. By increasing/decreasing the resistance, the light affects the current, or the amount of charge over time. Ohm's law, I=V/R demonstrates this because if R is higher, than I is lower.

 Less current means less power, as shown by the equation P=IV. So because V is a constant 120V (from the outlet),  current is the only thing that affects the power. By increasing current, I can increase the power and brightness of the light, or by decreasing the current, I make the bright dimmer.

Physics Blog #8 Bigger is not always better

I was running out of ideas to do my physics blog when I saw this amazing scene outside. Theoretically, if buildings did not have lightning rods, it would be better to be a small building, as show in the picture. 

The bigger and taller buildings (that I pointed out) would be more prone to lightning strikes because they are closer to the polarized, negatively charged underside of clouds that want to be neutral (which explains why in the times before lightning rods, tall buildings were more frequently hit). So it would be better to be a small building because you are shielded by the bigger ones.

Luckily, somebody invented lightning rods, which prevent big buildings from being shocked. When lightning strikes, it hits the lightning rod and is harmlessly conducted into the ground by a wire.

I also found this funny cartoon that made me laugh a lot because i love physics.

(Late) Blog Torque!

This is a pool cleaner that we use at my house. I realized that the equation for torque, t=fr, applied to it.

In order to increase the amount of torque exerted I could lengthen my lever arm. For instance, the farther away my grip from the net, the more torque I have.

I could also increase my torque by increasing the force at which I swing the pool cleaner with.

Finally, I could also make the angle of my lever arm more perpendicular to the wrench, which would result in a larger r and therefore a larger F.

The moment of inertia concept also applies to the cleaner. If I grasp the cleaner closer to the netting, my moment of inertia would be smaller because my r or l is smaller. This also means that it would be harder to start or stop the pool cleaner.

(Late) Blog Static Equilibrium Light

This light demonstrates static equilibrium.  The combined tension in the two rods must be equal to the downward force of the lights and the wooden support. The resulting equation would look like:

T1sintheta+T2sintheta=mglight1+mglight2+mgwood

We can also know that because the light is at equilibrium, the net torque is 0. To find the net torque, we can use the equation Tccw (counter clockwise) -Tcw (clockwise)=T=0.

To solve the problem, you could use either end as the fulcrum. For instance, if the left side (when looking at the picture) was used as the fulcrum, than the equation would be:

T2y(r)=mglight1(r)+mglight2(r)+mgwood(r)

After finding T2y you could then find T1y.

Physics Swing Circular Motion Blog #5

This swing shown in this video displays several properties of physics.  If I had the variables, I could find it's linear acceleration, which is a change in speed.  The linear acceleration can be found by using the equation a=∆V/t.  Since the swing was also moving in a circular motion, it has centripetal acceleration too! In caveman terms, centripetal acceleration is a change in direction, which the swing is certainly doing. The equation for centripetal acceleration is ac=mv^2/r, or alternatively, ac=ω^2r. We can also find ω (wumbo) from the equation. Wumbo is the symbol for angular speed, which can be measured in rpm or rad/s. In other languages, wumbo also is a verb and a noun.

If I have wumbo, then I can also find my linear velocity using the equation v=rω. The swing has linear velocity, linear acceleration, angular speed, and angular velocity. Next time I go on it, I will try to increase my velocity by increasing my rpm (ω) as well as my radius.

Physics, Anger, Energy Blog #4

Today, I was really angry that I bombed my physics test. In order to release my anger I threw a real cow at a surfboard. I felt sorry for the surfboard afterwards. The cow was okay though.

The formula for work is W=F*displacementX(costheta).  Where W is work and F is the force.  So by finding the distance traveled by the cow and the force my cannon arm applied to the cow, I could find the work done.

By finding the work done, I can also find the velocity of the cow. Unfortunately my cow was a baby and weighed too little to be registered on the scale, but by using the formula: W=KEf+0 (because there is no initial KE), because KE is 1/2*m*v^2, I could find the velocity. Alternatively, I could find the weight if I had the velocity. However, I think that even though this cow seemed to weigh a ton, the velocity would be too high for me to calculate due to the enormous amount of work done.

I could also calculate my power by dividing my work done by the time it took for the cow to hit the surfboard (.000009s?). P=J/t. Then I could find my horsepower by dividing the power (in watts) by 746...but that would be too much WORK for me to do...

Swing: Newton's Third Law

 

Newton's third law states that for every action, there is an equal and opposite reaction.  Meaning that if A pushes B with x amount of force, than B pushes back with x amount of force, or, if A pulls B with x amount of force, than B pulls A with x amount of force.

In this video I demonstrate Newton's third law.  I push the swing with x amount of force, causing it to go forward (the direction I push), the swing pushes back at me with an equal amount of force.  However, the swing moves more because it accelerates more.  Using Newton's Second Law's equation (a=net force/mass), it makes more sense.  Since the swing has a lot less mass than me, it accelerates more.  But, because I comparatively have a lot more mass, my acceleration (backwards) is very small.

Post #2: Garage Door Acceleration

 

 

I was thinking of what to do for my next physics post when I came home.  As soon as the garage door opened, I realized that the answer was right in front of me! The garage door opening or closing demonstrates acceleration! Unfortunately, I can't find the acceleration without the elapsed time or the velocity, because the formula for acceleration is a=v/t. First, I took a video of the garage door closing and found that it took about 14 seconds to close completely.  Then I took the height and found that it was about 8 feet, or 2.43 meters, since the door only went down, the displacement is also 2.43 meters. Using this information, I could find the velocity, v=2.43m/14s, v=.17 m/s. Since I have my velocity and my elapsed time, I can now find the acceleration of my garage door!
a=.17 m/s /14, a=.012 m/s^2. Wow, that's a fast door!

Using physics, I was able to discover the acceleration of my garage door. First, I needed to find the velocity, which was accomplished by finding the displacement (2.43m) and the time (14s). Then I was able to plug these numbers into the equation for acceleration.

Swimming in the Pool: Distance and Displacement

me entering the pool

Today, I went swimming in my pool. I began by the steps on the right of the picture and swam to the end of the pool on the left. I count one lap as going to the end and coming back. After I did five laps in the pool I got out.  I started at about 4:55 and stopped at 4:57 with 10 seconds left.  So it took 130 seconds.  The length of my pool is about 27 feet, or 9 meters.  In physics, I learned that distance is the magnitude, or the amount of the displacement.  Therefore, one total lap is equal to 9m*2, and 5 laps is equal to 5(9m*2), which is equal to 90 meters.  Since I calculated the distance, I can plug it in to the formula we learned in class for average speed.  The formula is distance/time=speed. 90 meters/130 seconds=.69 m/s. So I swam about .69 meters per second.

I could also use this data to find my average velocity. We learned that the formula for average velocity is: displacement/time=velocity.  Displacement differs from speed because it is the "shortest path from the initial to the final position of the object's motion." In order to find my displacement, I used the formula: x final-x initial=displacement.  Therefore, the displacement for one lap is equal to 9m - 9m=0m +/- .  0m/130 seconds=0 m/s +/- . My average velocity is 0 because I had 0 displacement due to just swimming back and forth.

Physics taught me that velocity is different from speed because velocity includes the speed and direction of the object's motion.  Swimming laps in the pool proves that speed and velocity are different. By finding the length of the pool and the time it took to swim 5 laps, I was able to gather the data necessary to calculate both speed and velocity.