# sara329

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## Blog Entries posted by sara329

When light is hitting you it is actually waves or particles of matter. This is because light is matter and light is waves.

Young's double slit experiment is what can prove light is a wave. He projected light through walls with two narrow slits in them. The result on the wall behind is interference patterns which shows that when the waves of light go through the slits they interfere and cross each other. This also shows diffraction which is the bending of waves around obstacles or spreading of waves when they pass through an opening. Another thing that proves light is a wave is red and blue shifts. When a star is moving very quickly at us it appears to us bluer than it actually is because the wavelength decreases.

The Compton effect proved that light is a particle because it shows that light has momentum.The photo electric effect is when light is shined at a thin piece of metal the photons knock electrons out of the metal. This shows that electrons are pieces of matter because they have momentum.
My friends and I go to Zumba classes three times a week and it is very fun. Like any regular physics student, I am constantly thinking about Mr. Fullerton's lessons during class. As we dance, jump, and move I get to thinking... it must take a lot of energy to move around the way we do. But as we eat healthily and exercise more often, Zumba gets easier and easier... why?

Here are some of the equations I will be using to help explain this Zumba Paradox...

- KE = (1/2)(mass)(velocity2)
- PE = (mass)(g)(height)
- Work = Change in Mechanical Energy
- Work = Force * Displacement

It takes work to move our body in all different sorts of ways. Because work is equal to the change in Mechanical Energy, and both Kinetic Energy and Potential Energy are proportional to the mass of the object, it is reasonable to say that work is also proportional to the mass of the object. In this case, the object is our body.

As any athletic trainer will happily tell you, a good workout is one where you do the most work. In our case, we will hold everything else constant besides our mass because we are doing the exact same class every time we work out. Put extremely simply, work is how much you move times how much weight you are moving. So, it is correct to say that as you lose mass you will do less and less work each successive time you go to Zumba class.

I want to lose weight at a constant rate, as would most females in Zumba class. Constant weight loss is much better than fluctuating weight loss. So how can I keep my weight loss constant, and overcome this work-mass relationship that we discussed earlier?

Zumba deals with changes in Kinetic Energy more than other types of fitness training such as weight lifting which deals more with changes in Potential Energy. So for simplicity we will set Work equal to the change in only KE.

Here's what we want to happen:

C = (1/2)(mass)(velocity2) // With C being a constant positive number that represents an amount of Joules

In order for us to keep a constant C, velocity2 has to increase at a rate equal to the rate at which mass decreases.

Here's our relationship in equation form:

velocity2 = 1/mass // or in exponential form --> velocity = mass-1/2

So there it is, ladies and gents, if you want to lose weight at a constant rate, you need to increase your intensity a little bit each class as you shed the pounds.
I'm assuming that many people have been to a concert or obviously heard music before. While listening or being at a live music show people are usually not thinking about all the waves that are hitting them and going into their ears, at least i never do. But once you think about it, it is very weird to realize that sound isn't just sound; it is waves.

Sound waves to be exact are longitudinal waves which means the wave consists of compression's and rarefaction's and the vibrations are in the same direction as the waves travel. Sound waves are also known as mechanical waves so they always need a medium to travel through so a concert would definitely would not work in outer space!

Amplitude and frequency are the major parts of what makes a concert possible. The speakers need to be turned up to the right amplitude and frequency in order for the music to sound good. The waves amplitude will be larger for the sound to be louder. Also for a lower frequency depending on the type of music the wavelength will control the frequency. The longer the wave length the lower.

Last if you ever wondered about why you can hear music even if a door is separating you from a radio or a concert is happening far away from you, this is because waves are able to diffract or bend around obstacles or spread through an opening.

So next time when you are at a concert just think about all the waves that are around you!
Recently I watched Lords of Dogtown, and I noticed that surfing has a lot to do with Physics...

Kinetic Energy of Waves:

Oceanic Waves hold a lot of kinetic energy which is transferred to the surfer as they ride - propelling the surfer forward. This kinetic energy in the waves is dependent on the height of the wave (a.k.a. the amplitude of the wave).

The relationship can be written as: Energy = c * Amplitude2 (where c is a constant)

Centripetal Force when Carving:

Surfers turn sharply when they ride a wave and this is called "carving". Also, the coefficient of friction on water is very low. This results in a lot of sliding around. So when surfers "carve" they aren't necessarily changing the vector component of their momentum.

This equation can be modeled as: Fc = (mass*velocity2) / radius of turn
The average surfer has a mass of 65kg, is traveling a speed of 15 m/s, and is turning on a radius of
less than 2 meters... This results in a very high centripetal force.

Transverse Nature of Oceanic Waves:

Ocean waves are a type of transverse wave. Though they do not resemble a normal sine wave... they more resemble a transverse than longitudinal wave. The actual H2O molecules do not move along with the wave but are rather just moving up and down like electrons in a light wave.
Recently I saw the movie 42 about the legendary baseball player Jackie Robinson. Even though I am not a baseball fan it was still a really good movie. While I was watching i realized how much baseball really has to do with physics. Then when we watched a video in class about baseball relates with physics I was amazed! Baseball involves velocity, force, and projectile motion and many more aspects of physics.

Also pitching involves momentum. Basically before the pitcher throws the ball his momentum moves from his legs (the larger parts of his body) up through his fingers (the smaller parts of the body) into the ball. This gives the ball velocity and momentum while it travels through the air. Momentum travels through the body constantly trying to make the ball go faster.

Newtons 2nd law f=ma also relates to baseball. The harder the throw the faster the ball. Each pitch is fighting against gravity and friction; the air slows it down. However gravity and friction makes the ball do certain things like a curve ball. The ball spins from finger pressure; the direction the ball is spinning is the way it will curve.

Newtons third law, or every action there is an equal and opposite reaction is also involved. However much force the batter has, that's how much force the ball will have after it hits the bat. So, obviously the batter wants to hit it hard. The batter has less than .5 seconds to swing. The heavier the bat the harder it is to get it to move fast but the heavier the bat the faster the ball will go when hit. When the ball its the bat, oddly, it squishes up to about half its normal size and gains potential energy, then it springs back off the bat with equal the force that it was hit with.

Lastly the sweet spot on the bat relates to nodes of a wave. If the batter swings and the ball hits at the "sweet spot" of the bat (a node) their will be less vibration of the bat. If the batter hits the ball at an anti node their will be too much vibration which is bad.

Anyways it was very interesting for me to learn all about how baseball relates to physics, hope it was interesting for you too!

Jackie Robinson

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