A 4.0 kg ball is traveling at 5.0 m/s to the right and strikes a wall. The ball bounces off the wall with a velocity of 4.0 m/s to the left. The change in momentum of the ball is
A) 4.0 kg m/s left.
B) 36 kg m/s right.
C) 26 kg m/s left.
D) 30 kg m/s right.
E) 36 kg m/s left.

Question

Quizplus · Accepted Answer

The change in momentum ($\Delta p$) is calculated using the formula $\Delta p = m(v_f - v_i)$, where $m$ is the mass, $v_f$ is the final velocity, and $v_i$ is the initial velocity. Here, $v_f = -4.0 \, \text{m/s}$ (to the left, hence negative) and $v_i = 5.0 \, \text{m/s}$ (to the right, hence positive), so $\Delta p = 4.0 \, \text{kg} \times (-4.0 - 5.0) \, \text{m/s} = -36 \, \text{kg m/s}$, which means a change of 36 kg m/s to the left.

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