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Mechanics
 Aim: to estimate the Coefficient of Restitution for a ball bouncing on the laboratory bench When two objects collide, their coefficient of restitution gives a measure of the elasticity of the collision. An totally elastic collision is one in which kinetic energy is conserved. In practice some k.e. is always converted into other forms. Which other forms? If we compare the relative velocity of the two objects just before the collision (velocity of approach, va) with their relative velocity just after the collision (velocity of separation, vs) we can see "how elastic" the collision was. We therefore define the quantity the coefficient of restitution, e as follows To use a sophisticated technical term, we are going to find out how bouncy the ball is! Notice that e = 1 corresponds to a perfectly elastic and e = 0 a totally inelastic collision (the objects stick together). Method In order to estimate the height h2 to which the ball bounces, it is helpful to have two horizontal bars of adjustable positions, as shown below. An alternative method might be to video the ball in front of a background with some kind of grid marked on it... By considering energy changes during the fall of the ball (gravitational potential energy to kinetic energy) and during the rebound of the ball (k.e. to g.p.e.), you will see how a value for e can be taken from a graph of h2 against h1.

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