Here's why:
* Gravity: When a ball is thrown upwards, gravity constantly acts on it, slowing it down.
* Maximum Height: At the highest point, the ball momentarily stops moving upwards. This is because gravity has completely counteracted the initial upward velocity.
* Changing Direction: The ball is about to start falling back down, meaning its velocity is changing from upward to downward. At the instant it reaches the highest point, the velocity is zero as it transitions between these directions.
