Understanding the Concepts

* Projectile Motion: The ball is a projectile, meaning its motion is governed by gravity.

* Acceleration due to Gravity: The acceleration due to gravity (g) is approximately 9.8 m/s², acting downwards. This means the ball's velocity decreases as it travels upwards.

* Highest Point: At the highest point, the ball's vertical velocity momentarily becomes zero.

Solving the Problem

1. Acceleration at the Highest Point: The acceleration of the ball at the highest point is still 9.8 m/s² downwards. Even though the velocity is zero for an instant, gravity is constantly acting on the ball.

2. Important Note: It's crucial to understand that the ball's *speed* changes, but its *acceleration* remains constant throughout its flight (neglecting air resistance).

In Summary:

The highest point of the ball's trajectory is where its velocity is zero, but its acceleration remains a constant 9.8 m/s² downwards due to gravity.