Question

A tennis ball is traveling at 23 m/s across the court in a straight line. It meets a player's racquet and rebounds exactly reversing its direction with a speed of 18 m/s. The racquet is in contact with the ball for 11.5 ms. What is the magnitude of the ball's average acceleration abile it is in contact with the racquet?

Answer 1

From Newton's laws, we know that rate of change of momentum means change in momentum with respect to time is defined as force.

    

here p is change in mometum i.e p = p_f - p_i and p = m.v

Let us suppose mass of tennis ball is "m", so p is

p = m.v_f - m.v_i = m ( v_f - v_i )

p = (m) ( 18 - 23 )m/s = (- 5 m ) kg.m/s

So, from equation (1) we get

F = (-5.m) / 0.0115 = -(434.78 m) Newton

Ball average acceleration,

F = m .a = - 434.78. m

So, average acceleration = - 434.78

Here negative sign indicates that ball is deaccelerated after contact with racquet.