Question

Imagine that you throw a tennis ball vertically into the air. At the exact top of its trajectory it is at rest. What is the magnitude of its acceleration at this point?

I know that the answer is 9.8 m/s^2 but I want an explanation in terms of Physics please.

Answer 1

when we throw ball force due to gravity is always working on the ball. so when you throw it up due to gravitational acceleration downward its velocity decreases and it becomes zero at highest point and ball starts descending with increasing velocity. at top most point ball become stationary but still gravitational force is working on it. so its acceleration is same as gravitational acceleration 9.8m/s^2. It stops at highest point but gravitational force is still there so net force on ball is mg and its acceleration = mg/g = g.