Question

A tennis ball is thrown vertically upward with an initial velocity of +8.0 m/s. What will the ball's speed be when it returns to its starting point?

Answer 1

As the ball rises, its velocity decreases at a rate equal to 9.8 m/s^2 which is the gravitational acceleration.

At the highest point, the velocity of the ball is 0. It then starts to fall down and reaches the ground in the same duration of time it took to rise to the highest point. The velocity of the ball is equal in magnitude to the velocity it was thrown up but opposite in direction.

This gives the velocity of the ball when it returns to the starting point as -7.7 m/s

The time taken by the ball is 2*(7.7/9.8) = 1.57 seconds

Answer 2

Final speed of the ball, v = -8 m/s

Step-by-step explanation:

It is given that,

Initial velocity of the ball, u = +8 m/s

Let v is the speed of the ball when it returns to its starting point. When it returns back to its starting point, the speed of the ball remains the same only its direction changes.

Let positive direction shows upward side and negative direction shows the downward side. So, the speed of the ball when it returns to its starting point is (-8 m/s).

Hence, this is the required solution.