A cricket ball of mass 200 g moving with a speed of 40 ms−1 is brought to rest by a player in 0.04s. Calculate the following :
(i) change in momentum of the ball,
(ii) average force applied by the player. [2 MARKS]
Solution:2 Marks
Mass, m=200g=0.2 kg
Initial velocity, u=40 ms−1
Final velocity, v=0
Time, t=0.04 s
Initial momentum, p1=m×u=0.2×40=8 kgms−1
Final momentum, p2=m×v=0.2×0=0
Change in momentum, p=p2−p1=0−8=−8 kgms−1
Average force=m×(v−u)t=0.2×(0−40)0.04−200N
The negative sign shows that the force is applied in a direction opposite to the direction of motion of the ball.