| 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 or 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 conservation of energy | the law that states that energy is neither created nor destroyed. |
| energy resource | a natural resource that can be converted by humans into other forms of energy in order to do useful work. |
| nonrenewable resources | natural resources that cannot be replaced or that can be replaced only over thousands or millions of years. |
| fossil fuels | nonrenewable energy resources that form in the Earth’s crust over millions of years form the buried remains of once living organisms. |
| renewable resources | natural resources that can be used and replaced over a relatively short time. |
