Read each statement below carefully and state with reasons and examples, if it is true or false;

(a) True
(b) False
(c) True
(d) False

Explanation:
When an object is thrown vertically up in the air, its speed becomes zero at maximum height. However, it has acceleration equal to the acceleration due to gravity (g) that acts in the downward direction at that point. Speed is the magnitude of velocity. When speed is zero, the magnitude of velocity along with the velocity is zero.

A car moving on a straight highway with constant speed will have constant velocity. Since acceleration is defined as the rate of change of velocity, acceleration of the car is also zero. 

This statement is false in the situation when acceleration is positive and velocity is negative at the instant time taken as origin. Then, for all the time before velocity becomes zero, there is slowing down of the particle. Such a case happens when a particle is projected upwards.

This statement is true when both velocity and acceleration are positive, at the instant time taken as origin. Such a case happens when a particle is moving with positive acceleration or falling vertically downwards from a height.

1. True:

Consider a ball thrown vertically, upward. At the highest point, the speed is zero but the acceleration of the ball is non-zero (9.8ms^-2 vertically downwards). Acceleration does not depend on instantaneous speed.

2. False:

Since the magnitude of velocity is speed, a body with zero speed must have zero velocity.

3. True:

In the case of a body rebounding with the same speed, the acceleration at the time of impact is infinite, which is not practical physically.

4. False:

This depends on the chosen positive direction. The statement is true when the direction of motion and acceleration are along the chosen positive direction.