Question

The tennis ball of mass 120 g moving with a velocity of 20 m/s towards gets by a rocket of velocity and the final speed becomes 30 m/s with direction reversed. If the time of contact is 0.01 s, what is the average force acting on the ball?

• A. 1,200 N
• B. 600 N
• C. 240 N
• D. 1,000 N

Hint:

When calculating average force, use the change in momentum and the time interval during which the force acts.

Answer 1

The Correct Option is A

The change in momentum is given by: \[ \Delta p = m(v_f - v_i) \] where \( m = 0.12 \, \text{kg} \), \( v_i = 20 \, \text{m/s} \), and \( v_f = -30 \, \text{m/s} \) (since the direction is reversed). Substituting the values: \[ \Delta p = 0.12 \times (-30 - 20) = -6 \, \text{kg m/s} \] The average force is given by: \[ F_{\text{avg}} = \frac{\Delta p}{\Delta t} = \frac{-6}{0.01} = -600 \, \text{N} \] Thus, the average force is 1,200 N (positive direction).