Question

Refer to the image. Calculate the magnitude of change in velocity of the cue ball.

The answer is 2.83 m/s. Please explain the step.

Answer 1

If you add the 2 velocity vectors you get the velocity of the third vector which is the (change in) velocity of the cue ball after striking the cushion

V * 2 * cos 45 = 4 * cos 45 = 2.83 m/s