1. Gaining Momentum

2.  Apart from the time it takes for a collision to occur, the size of an impact depends on the velocity and the mass of the objects involved.  A moving object with a large mass requires a larger force to stop it moving than a moving object with a small mass.  For example, a truck is much harder to stop than a smaller Toyota Corolla.

3.  In order to stop a moving vehicle, you must reduce its momentum.  Momentum (p) is a measure of an object’s movement. It is the product of its mass (m) and velocity (v): p = m × v (kg m/s)=(kg)x(m/s)

4.  In a collision, momentum is passed on from one object to another.  The law of conservation of momentum states that the total momentum of a system won’t change unless an external force acts on the system.  In this case, the total momentum after the collision is the same as the total momentum before the collision. p before = p after

5.  For instance, a train carriage moving along at 12 m/s links up with another identical carriage that was stationary and the two keep moving. It is as if the first carriage has suddenly doubled its mass. The two carriages together have the same momentum as the one that was originally moving by itself. Since the mass is doubled, the velocity will halve. The two carriages will move along at 6 m/s.

6. Having a ball!