Question

A ball was dropped from a certain height and reached a speed of 1.0m/s just before it hit the ground. It then rebounded with a speed of 0.80m/s. What was the change in the ball's momentum if the ball has a mass of 200 grams?

Answer 1

Let us consider the upwards direction as positive and the downwards direction as negative.

Mass of the ball = m = 200 g = 0.2 kg

Initial velocity of the ball just before it hits the ground = V₁ = -1 m/s

Initial momentum of the ball = P₁

P₁ = mV₁

P₁ = (0.2)(-1)

P₁ = -0.2 kg.m/s

Velocity of the ball after rebounding off the ground = V₂ = 0.8 m/s

Final momentum of the ball = P₂

P₂ = mV₂

P₂ = (0.2)(0.8)

P₂ = 0.16 kg.m/s

Change in momentum of the ball = P

P = P₂ - P₁

P = 0.16 - (-0.2)

P = 0.36 kg.m/s

Change in momentum of he ball = 0.36 kg.m/s