A student standing on the ground next to a tall building throws a ball straight up with a speed of 39.2 m/s. If it takes the ball 4 seconds to reach the same height as the top of the building, how tall is the building?

Question

Physics

Lyons

4 March, 22:54

A student standing on the ground next to a tall building throws a ball straight up with a speed of 39.2 m/s. If it takes the ball 4 seconds to reach the same height as the top of the building, how tall is the building?

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Answers (1)

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Irvin Crosby · Answer 1

Using the equation of motion:

h = ut - 0.5gt²,

g is - ve for a rising body, g ≈ 10 m/s², t = 4s, u = 39.2m/s

Note that in this problem we are neglecting the height of the student.

h = ut - 0.5gt²,

h = 39.2*4 - 0.5*10*4² Use a calculator

h = 76.8 m

The building is 76.8 m tall.