Question

19. State with example
(a) With zero speed at an instant may have non-zero acceleration at that instant
(b) With zero speed may have non-zero velocity?​

Answer 1

Answer:

a) When a particle moves with a constant speed in the same direction, neither the magnitude nor the direction of velocity changes and so acceleration is zero. In case a particle rebounds instantly with the same speed, its acceleration will be infinite which is physically not possible.

b) When a body begins to fall freely under gravity, its speed is zero but it has non-zero acceleration of