Question

A ball is thrown straight upwards from the top of a building with a velocity of 15 m/s. The building is 21 m high and the ball just misses the edge of the roof on its way down. What is the maximum height reached by the ball?

1) 15 m
2) 21 m
3) 30 m
4) cannot be determined

Answer 1

The maximum height reached by the ball is 32.47 m.

Step-by-step explanation:

To find the maximum height reached by the ball, we can use kinematic equations. We know that the initial velocity of the ball is 15 m/s and the height of the building is 21 m. When the ball reaches its maximum height, its final velocity will be 0 m/s. Using the equation v^2 = u^2 + 2as, where v is the final velocity, u is the initial velocity, a is the acceleration, and s is the displacement, we can solve for the displacement:

0^2 = 15^2 + 2(-9.8)s

s = 11.47 m

Since the ball just misses the edge of the roof on its way down, the maximum height reached by the ball is 21 m + 11.47 m = 32.47 m.

Therefore, the correct answer is 3) 30 m.