Consider the inelastic collision of two masses m and m2. Use a zero-momentum reference frame (essentially a frame co-moving with the centre of mass of the system) for which m m = 0 m1v1 m2v2 = 0 , (1) holds. Show that the square of the coefficient of restitution e is equal to the ratio between the kinetic energy after the collision and the kinetic energy before the collision in the zero-momentum frame. Express e in terms of Q (energy lost in the collision) and the initial velocities u and u only.