Assertion : Acceleration of a moving particle can change its...

Assertion is false: Acceleration is the rate of change of velocity. If the direction of velocity remains unchanged, it means the motion is along a straight line without any change in direction. In such a case, for acceleration to change direction, the velocity would also have to change its direction, which contradicts the assertion. For example, in projectile motion, acceleration (due to gravity) is constant downwards, but the velocity vector continuously changes direction. Reason is true: Acceleration is defined as (\Delta \mathrm{v} / \Delta \mathrm{t}). If the direction of the change in velocity vector ((\Delta \mathrm{v})) changes, then the direction of the acceleration vector (a) also changes.