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COLLISIONS

Elastic collisions

In a collision the kinetic energy is sometimes the same before the collision as it is afterwards - such a collision is called an elastic collision. Perfectly elastic collisions are rare - usually some of the kinetic energy is converted to sound or heat.

Inelastic collisions

A perfectly inelastic collision is one where all the kinetic energy is converted into other forms - a piece of soft putty falling onto the floor is an almost perfectly inelastic collision, the kinetic energy of the moving putty is converted into heat and a little sound as the putty is deformed on impact.

Most real collisions are usually somewhere between the two extremes.

In all collisions the law of conservation of momentum applies. The total momentum before collision must be equal to the total momentum after collision. If we know the masses and velocities of the colliding objects before collision we can use this principle to find out how fast they are moving - and in which direction - after the collision.

 
 
 
© Keith Gibbs 2011