Assertion : A body is momentarily at rest at the instant it reverses the direction. Reason : A body cannot have acceleration if its velocity is zero at a given instant of time.

Step-by-step solution

Assertion is true: When a body reverses its direction of motion, its instantaneous velocity must be zero at that point (e.g., a ball thrown upwards momentarily stops at the peak before falling). Reason is false: A body can have acceleration even if its velocity is zero at a given instant. For example, a ball thrown vertically upwards has zero velocity at its highest point, but its acceleration is still ' g ' (acceleration due to gravity).