Spark image

Newton's Law of impact

Newton described the elasticity of the collision by considering the velocities of approach and recession as shown in the following diagram.



Velocity of approach = u u'
Velocity of recession = v' v

He defined a quantity known as the coefficient of resititution (e) as:

Coefficient of resititution (e) = [v v]/[u u]

This is known as Newton's Law of impact.

The ratio [v' v]/[u' u] must always be less than one except for a perfectly elastic collision where it is equal to 1. For a perfectly inelatic collision e = 0.

This means that in a perfectly elastic collision the velocity of approach of the two bodies before the impact is equal to their velocity of separation after the impact.


For an experiment to measure the coeffcient of restitution see: 16-19/Properties of matter/Elasticity/Experiment guides/Coefficient of restitution
 

A VERSION IN WORD IS AVAILABLE ON THE SCHOOLPHYSICS USB
 
 
 
 
© Keith Gibbs 2020