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As I've been reviewing for midterms, i've noticed how related all the different areas of physics we've studied are. You could potentially make a problem that involves almost every concept we've covered.

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[mattturchioe-deactivated2014091]

Recently we’ve been learning about thermaldynamics and it’s presence in the world. One example would be the refrigerator in your kitchen. It has a hot and cold side that constantly switch by doing work, moving the hot away from the cold so your food doesn’t spoil. It’s interesting to see how these universal laws are present in the simplest of things

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Its also interesting to note how all those simple things interact in one giant system. The refrigerator iteracts with the air, which interacts with the walls, with the ground, etc. 

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I know I've done this before but I can't help doing it again. Seriously guys, WATCH THIS GUY'S VIDEOS. His explanations are both easy to understand and very robust. Here he explains potential energy within a spring. 

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The compound bow is a prime example of mechanical advantage, which I assume we will be learning more about in class. The archer begins with a mechanical disadvantage in relation to the limbs of the bow, and has to pull the string back with a large amount of force. As he pulls however, the pulleys turn, and the archer begins to gain a mechanical advantage over the limbs. This allows the archer to store up greater energy, and hold it for a longer amount of time, than he would be able to with a recurve or longbow. 

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Today we did a lab concerning mechanical advantage and pulleys. We set up a weight connected to a system of pulleys three times. Each time we pulled the string taut, and measured its length. Then we pulled it up to a previous mark and measured the length again. Then we found Ama and Ima, and solved for the systems efficiency. As a whole the lab demonstrated mechanical advantage and why pulleys are so useful in physics

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It was interesting to note that while pulleys decreased the amount of force necessary to lift the weight, they also decreased the efficiency of the entire system. 

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Today we did a lab involving pulleys. We used pulley's to demonstrate the concept of energy efficiency. We found that the more friction that was introduced into the system, the less efficient it became. 

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Muscles contain potential energy-stored up in chemical bonds. When those bonds are broken down, that energy is converted into kinetic energy etc. Muscles also relate to what we have been talking about in class in another way. High-mass muscles, such as those on Schwarzenegger, have a tremendous amount of strength, and thus can do large amount of work. This does not mean they have a lot of power though, or "explosiveness" in athletic terms. This is why athletes, as opposed to bodybuilders, do plyometric exercises - exercises which decrease the time their muscles need to do the same amount of work. This allows players to jump high, sprint, make a tackle, etc. 

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The photo above is of an 800hp engine, such as might be used in a high-power sport car. 

As we discussed in class, the increased power does not increase the magnitude of work (distance travelled or load carried in this case) the car can do, only how fast it can do it. Which of course makes one question why people really want such high-powered cars. Speed-limits kind of defeat the purpose....

[canyoubelievethisurlwasavai-blog]

So today we decided to talk about bullets and the difference between full metal jacket (FMJ) rounds and hollow point (HP) rounds. The difference is (surprise!) the HP round has a hollowed section. When the bullet strikes a soft target, a tremendous amount of pressure builds up and the bullet expands. This deals a great amount of damage to soft(unarmored) targets but can have difficulty penetrating anything else. The HP round typically should not fragment, and to ensure it doesn’t some rounds are “jacketed” with copper or steel. If the round does fragment it can hardly penetrate anything.

Anyway, kids, remember to use your knowledge for good and not for evil!

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I wonder if the hollow point has any effect on the path/accuracy of the bullet?

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In class we have been discussing work and power. I thought an interesting way of explaining power was as follows. Impulse is force over time. Work is force over a distance. Power is a force over a distance over time. In this sense, power is almost the combination of work and impulse.

[canyoubelievethisurlwasavai-blog]

Impulse is a vector. It can be defined as the force acting on an object times the time during which the force is exerted. The equation is J(impulse)=f▲t. Either parts of the previous equation can be set equal to ▲p(momentum). Because of this, a small force applied for a large amount of time can cause the same changes that a large force can over a short amount of time.

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good explanation, but how did you get the little delta symbol? 

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In class, Mr. Love said we wouldn't be going into two-dimensional momentum problems, as they were too complicated. But, if you are still interested, Khan Academy once again delivers an extremely simple to understand lecture in the subject.

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Perpetual motion is an interesting idea, though currently considered impossible. The basic idea behind this is that there is not such thing as a system which does not lose energy. This is because of the laws of thermodynamics, which I am sure we will get to at some point in class. So while we have been discussing "perfect" systems for our momentum collisions, the perpetual collisions representing by the program cannot actually exist. The wiki article goes into further detail. 

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This is a video of various things that can be done with Newton's Cradle, all of which represent conservation and transfer of momentum. 

[mattturchioe-deactivated2014091]

A popular act of hooligans on thanksgiving is to stand above a highway and drop turkeys on the passing cars. While its hilarious, its also costly and dangerous. The turkey accelerates downward at 9.8m/s^2 and it will most likely crush and bounce off of the windshield or hood of the car, transfering its momentum to the car. Not only is it a waste of a good turkey, but its dangerous in the sense that drivers are shocked by the collision, and can loose control.

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This example also shows how complicated real-world physics actually is. The turkey would probably bounce off, in spite of a large amount of its kinetic energy being lost in the crushing of the windshield, which produces heat energy.

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This video is incredible, but it also shows the conservation of momentum.