| A | B |
|---|
| People in ancient times used a _____ and a shadow created by the sun to tell time | sundial |
| anything that moves something else | force |
| sight or visible waves of light | optic |
| The force that pulls objects towards each other | gravity |
| When light bends as it passes through a different material | refraction |
| speed of motion | velocity |
| A force that keeps objects from sliding easily | Friction |
| top of a wave | crest |
| bottom of a wave | trough |
| number of vibrations in a wave, in a given time | frequency |
| an up & down movement | wave |
| any change of position | motion |
| the distance from one point of a wave to the same point on the next wave | wavelength |
