* Acceleration is the rate of change of velocity. It describes how quickly and in what direction the velocity is changing.

* Constant acceleration doesn't mean constant velocity. Imagine throwing a ball straight up in the air. The acceleration due to gravity is constant (approximately 9.8 m/s² downwards). However, the ball's velocity changes:

* Going up: The velocity is positive and decreasing (slowing down) as the ball moves upwards against gravity.

* At the peak: For a split second, the velocity is zero as the ball changes direction.

* Coming down: The velocity is now negative and increasing (speeding up) as gravity pulls the ball back down.

In summary: Constant acceleration can cause a change in velocity's direction, leading to a reversal of the velocity.