Q. A ball hits a vertical wall horizontally at $10\ m/s$ bounces back at $10\ m/s$
A) There is no acceleration because $10\frac{m}{s} - 10\frac{m}{s} = 0$
B) There may be an acceleration because its initial direction is horizontal
C) There is an acceleration because there is a momentum change
D) Even though there is no change in momentum there is a change in direction. Hence it has an acceleration
Explanation
(c) As the ball bounces back with same speed so change in momentum $= 2\ mv$
And we know that force = rate of change of momentum
$i.e.$ force will act on the ball so there is an acceleration
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.