You always remember these rules . . . you dream them at night, you use them to solve your homework problems, you recite them to yourself on your way into a test, you use them to solve the test problems, and you never forget them:
1). The amount of work done is (Force) times (distance the force acts).
2). Work is energy. The amount of energy never changes. There's no way to create it, and there's no way to destroy it. Energy never just appears or disappears. If suddenly there's more energy, it came from somewhere. If suddenly there's less energy, it went somewhere. If you put some energy into a container that energy can't penetrate, then the amount of energy inside the container never changes.
3). Work is energy. So you can use energy to do work, and you can do work to provide energy for something.
4). Power is how much work is done in one second, or how much energy moves to a different place in one second.
