Collisions

A collision occurs when two or more objects come into contact with each other

Coefficient of Restitution: describes how objects bounce off each other after a collision

States the difference in velocities of the two objects is directly related to the difference in velocities before the collision

C = Vb - Va / Ua - Ub

Provides us with information about the elasticity of the collision

Dependent on what materials the objects colliding are made of

1.0 = perfectly elastic - no kinetic energy is lost, objects bounce off each other fully

0.8 - 0.99 = mostly elastic - some energy is lost, but most is conserved

0.5 - 9.7 = partially elastic - noticeable energy loss, not all motion is transferred

0.0 = perfectly inelastic - objects stick together after the collision, maximum energy lost

Example: in a snooker match, the white ball (Ball A) is moving at 2.4 m/s and strikes the red ball (Ball B), which is also moving in the same direction at 1.2 m/s.

After the collision:

The cue ball slows down to 1.0 m/s

The red ball speeds up to 2.0 m//s

Calculate the COR?

CR = (2.0 - 1.0)/(2.4 - 1.2) = (1.0/1.2) = 0.8333 (partially elastic)

Newton's Cradle

The coefficient of restitution is very close to one (almost perfect elastic collision)

• Very little energy is lost

• The momentum and kinetic energy transfer cleanly to the ball

Change in momentum is equal to the impulse applied to the object

Based on newtons second law