Question

A 3 kg ball strikes a heavy rigid wall with a speed of 10 m/s at an angle of 60°. It gets reflected with the same speed and angle as shown here. If the ball is in contact with the wall for 0.20s, what is the average force exerted on the ball by the wall?(a) 150 N(b) Zero(c) 150√3 N(d) 300 N

Answer 1

mass of the ball = 3Kg

velocity of the ball= 10m/s

velocity with which the ball is going towards wall (V-initial)= 10 cos60 = 5m/s

similarly, ball away from wall(V-final)= -10 cos60 = -5m/s

using eq.

Avg. Force = change in momentum/time interval

                  = (m)(v-initial) - (m)(v-final)/t

                  =(3)(-5) - (3)(5)/0.20s

                  =(-15)-15/0.2

                  =(-30)/0.2

                  =(-150N)

negative sign shows that force exerted by wall is in opposite direction.

hence , option A is correct