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Energy

Energy is the potential for change, or, the potential to do work. Something with energy can change, and something with out energy cannot. There are many types of energy; mechanical, electric, magnetic, gravitational, chemical, nuclear, and many others.

Quite possibly the most wondrous thing in all of science is this: if you add all of the different types of energy together, then for any given system, the total energy is conserved!

This means that the only way systems can run out of energy is by giving it up to other systems! (This is a bit deep for this class, but important all the same. Make of it what you will.)

In your lab notebook: Come up with three different systems. For each of your three systems, list as many different types of energy that you can think of that are a part of that system. (It is okay if you aren’t certain, give it a go!)

Table of contents

  1. Kinetic Energy
  2. Potential Energy
  3. Activity - Roller Coaster

Kinetic Energy

Kinetic means motion. Think of the XBox Kinect, it uses motion to control the XBox. That is also why Kinect is spelled that way, it is related to kinetic, not connect.

Kinetic energy then is the energy objects have because they are moving. If an object isn’t moving, the kinetic energy is zero. If it is moving, the kinetic energy is not zero.

The equation for kinetic energy is:

KE=12m×v2

Where m is the mass, v is the velocity. Bonus math question for you, because velocity is squared, does it matter if we use speed instead of velocity in this equation?

The important thing to note is the square. If you go twice as fast, you have 4 times as much energy! This is why speeding is so dangerous. When you go faster, you don’t get just get a little more energy you get a lot more energy.

Speaking of car crashes, doesn’t kinetic energy and momentum look really, really similar? p=mv and KE=12mv2. I mean, look, they have all the same pieces. The best way to figure out the difference is to remember, momentum only changes if an OUTSIDE force acts on the system, and the TOTAL energy is conserved. This means that if energy changes from one form to another in the system, you have to account for it.

In your lab notebook: In are car crash, are there any outside forces? So, is momentum conserved? Are there any other forms of energy involved in a car crash besides kinetic? If so what are they? Is total energy still conserved?

Potential Energy

Potential energy is the energy something has based on how far it can fall. If I pick up a bowling ball, that is hard, I’ll break out in a sweat. This means that I’ve done work, so I must have transfered some energy to the ball. The question is, what type of energy?

The ball isn’t moving after I pick it up, so it isn’t kinetic. The ball isn’t hotter after I pick it up, so it isn’t thermal. The ball isn’t electrically charged after I pick it up, so it isn’t electrical. You get the idea.

Turns out, just being moved higher is its own form of energy.

The equation for potential energy is:

PE=m×g×h

Where m is the mass, g is the acceleration due to gravity 9.8 m/s2, and h is the height off the ground.

Activity - Roller Coaster

You are going to have to wait. This is your assessment for this unit! So, see you next page!