Question

how do i solve this question?? A 100 g ball moving at a constant velocity of 200 cm/s strikes a 400 g ball that is at rest. After thecollision, the first ball rebounds straight back at 120 cm/s. Calculate:a) the final velocity of the second ball.b) If they were in contact for 0.1s, determine the magnitude of the force that acted on the second ball.

Answer 1

A.

$\begin{gathered} Momentum \\ m1v1+m2v2=m1v3+m2v4 \\ (100\cdot200)+0=(100\cdot-120)+(400\cdot v4) \\ 20000=-12000+400v4 \\ 32000=400v4 \\ v4=80cm/s \end{gathered}$

This is momentum conservation, is important to maintain the direction to know the positive and negative values

B.

$\begin{gathered} F=\frac{m(\Delta v)}{\Delta t} \\ F=\frac{0.4kg(0.8m/s)}{0.1s} \\ F=3.2N \end{gathered}$

For this part, is important to use the correct units. On A it was not relevant because you can use any units, you only have to maintain them the same.