| A | B |
|---|
| energy | the ability to do work |
| kinetic energy | the energy of motion; depends on speed and mass |
| potential energy | the energy of position of shape |
| mechanical energy | the total energy of motion and position of an object |
| energy conversion | a change from one form of energy into another |
| friction | a force that opposes motion between two surfaces that are touching |
| law of energy of conservation | the law that states that energy is neither created nor destroyed |
| energy resource | a natural resource that can be converted by haumans by humans into other forms of energy in order to do useful work |
| nonrenewable source | natural resources that cannot be replaced or that can be replaced only over thousands and millions of years |
| fossil fuels | nonrenewable sources that formin the Earth's crust over millions of years from the buried remains of once-living organisms |
| renewable sources | natural resources that can be used and replaced over a relatively short time |
