| A | B |
|---|
| mass | a measure of the amount of matter in an object; measured in g or kg |
| balanced forces | the forces acting on an object that cancel each other out so that the object is either stationary or moving at a constant speed in the same direction |
| unbalanced forces | forces acting on an object causing it to speed up, slow down or change direction |
| momentum | the tendency of the object to keep moving in the same direction |
| resultant force | the size of the overall force acting on an object |
| friction | a force that prevents objects from moving against each other easily |
| air resistance | resistance of an object to movement caused when it has to push air out of the way |
| drag | the resistance experienced by an object as is moves through a fluid, e.g. a boat in water or a plane in air; slows an object down |
| streamlined | shaped so that drag is kept to a minimum |
| terminal velocity | velocity at which a falling object moves through air, when the air resistance is equal and opposite in direction to the force of gravity |
| *propulsive force | the force that makes something move forward |
