A cement block accidentally falls from rest from the ledge of a 15.0m high building. When the block is 14.0m above the ground, a man who is 1.71m tall looks up and notices that the block is directly above him. How much time does he have to move out of the way?

Question

Physics

Eduardo Crosby

6 May, 13:37

A cement block accidentally falls from rest from the ledge of a 15.0m high building. When the block is 14.0m above the ground, a man who is 1.71m tall looks up and notices that the block is directly above him. How much time does he have to move out of the way?

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Yamilet · Answer 1

Given that,

For free falling body, acceleration is equal to acceleration due to gravity.

a = g = 9.81 m/s²

Distance to be covered, s = 15 - 1.71

s = 13.29 m

At top initial velocity, Vi = 0

Since,

s = Vi * t + 1/2 at²

13.29 = 0 + 0.5 * 9.81 * t²

t = 1.646 s

The man have 1.65 seconds to move out of the way.