Question

ㄐ-X. 19X A tennis ball with mass 0.06 kg moves toward a wall with a velocity of 20 m/s. The tennis ball bounces off a wall and then has a velocity of -20 m/s. If a force of 10 N is applied to the ball from the wall to change the balls direction, how long was the ball in contact with the wall?

Answer 1

$\\net\;force\;applied\;\left |F \right |=\left |\frac{\Delta P}{\Delta t} \right |=\left |\frac{m(v_f-v_i)}{\Delta t} \right |\\\\\\\\ 10=\left |\frac{0.06(-20-20)}{\Delta t} \right |\\\\\\ 10=\frac{0.06\times 40}{\Delta t}\\\\\\ \Delta t = \frac{2.4}{10}=0.24\;s$