A ball with original momentum +3.0 kg⋅m/s hits a wall and bounces straight back without losing any kinetic energy.The change in momentum of the ball is:

Question

Quizplus · Accepted Answer

According to the law of conservation of momentum, the total momentum before and after the collision is equal.

The initial momentum of the ball is +3.0 kg⋅m/s (since the direction is not specified, we assume it to be positive).

When the ball bounces straight back, it reverses its direction and hence its momentum becomes negative.

Therefore, the final momentum of the ball is -3.0 kg⋅m/s.

The change in momentum is the difference between the final and initial momentum, which is:

Δp = pf - pi 
Δp = (-3.0 kg⋅m/s) - (+3.0 kg⋅m/s) 
Δp = -6.0 kg⋅m/s

Therefore, the answer is D, -6.0 kg⋅m/s.

A Ball with Original Momentum +3