Q. A ball of mass $0.5\ kg$ moving with a velocity of $2\ m/sec$ strikes a wall normally and bounces back with the same speed. If the time of contact between the ball and the wall is one millisecond, the average force exerted by the wall on the ball is
A) $2000\ N$
B) $1000\ N$
C) $5000\ N$
D) $125\ N$
Explanation
(a) $F_{av} = \frac{\mathrm{\Delta}p}{\mathrm{\Delta}t} = \frac{mv - ( - mv)}{\mathrm{\Delta}t} = \frac{2mv}{\mathrm{\Delta}t} = \frac{2 \times 0.5 \times 2}{10^{- 3}} = 2000N$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.