Question

A ball of mass 1 kg elastically collides with a force plate over a time period of 0.1 s. If the magnitude measured on the force plate is 2000 N and the velocity before impact is four times less than the velocity after impact, in the opposite direct, what is the initial velocity of the ball?

160 m/s

40 m/s

267 m/s

67 m/s

Answer 1

force * time = impulse = change of momentum
2000 * 0.1 = 1 * (final V - initial V)
if direction is changed
200 = V - -.25 V = 1.25 V
V = 200 / 1.25