Read each statement below carefully and state with reasons and examples, if it is true or false, A particle in one-dimensional motion
(a) with zero speed at an instant may have non-zero acceleration at that instant
(b) with zero speed may have non-zero velocity
(c) with constant speed must have zero acceleration,
(d) with positive value of acceleration must be speeding up.

Explanation

True, E.g. : If object is thrown upwards, then speed will be zero at maximum height. But acceleration g = 9.8 `ms^(-2)` in downward direction.
(b) False. Because speed is magnitude of velocity. Hence speed is zero then velocity is also zero.
(c) True. When particle moves with constant speed in straight line, then velocity is constant. So the change in velocity is zero and hence acceleration is zero.
(d) False. The speed of object thrown upwards decreases. But if the speed and acceleration are in same direction, then its speed increases.