Sep 6, 2014

Momentum

The boulder, unfortunately has more
momentum than the runner
Momentum is the mass of an object multiplied by its velocity. The momentum of an object depends on its mass and velocity. This means that an object's momentum changes as it accelerates. Momentum can be transferred between objects. When a moving ball collides with a stationary one, for example, the first ball transfers some of its momentum to the second ball. The total momentum of the two balls is the same as the first ball's momentum before the collision. This is called the principle of conservation of momentum. 
(Dictionary of Science, by Neil Ardley)