| A | B |
|---|
| friction | the force that prevents objects moving against each other easily |
| lubricant | a substance that allows objects to move against each other more easily |
| braking distance | the distance taken for a vehicle to come to a stop after the driver puts the brakes on; also called stopping distance |
| streamline | to design an object so that it moves easily through air or water |
| air resistance | the force of air on an object that slows it down |
| speed | how fast an object moves |
| formula for speed | speed = distance / time |
| *motion | a change in an object’s position |
| *average speed | the distance an object has traveled in a given amount of time |
| *instantaneous speed | the speed of an object at a specific moment in time |
