physics
posted by farah .
an overhead view of the path taken by a 0.162 kg cue ball as it bounces from a rail of a pool table. The ball's initial speed is 1.11 m/s, and the angle è1 is 64.7°. The bounce reverses the y component of the ball's velocity but does not alter the x component. What are (a) angle è2 and (b) the magnitude of the change in the ball's linear momentum? (The fact that the ball rolls is irrelevant to the problem.)

Since one component of velocity stays the same and the other only changes sign, the kinetic energy (KE) does not change. That means the magnitude of the linear momentum, which is sqrt(2*KE*M), doesn't change either. The angle of reflection will equal the angle of incidence, but will be the supplement of 64.7 degrees (115.3 degrees) when measured from a common set of axes.