Question

A stone is droped from the roof of a building. it takes 4 second to reach ground. find the heigh of building ?

Answer 1

A stone is dropped from the roof of a building.it takes 4 sec to reach ground.
initial velocity of the stone , u = 0 m/s
time taken to reach the ground , t = 4sec
Let height of the building = h

now use formula, S = ut + 1/2 at²
here, u = 0, t = 4 and a = g = 10 m/s²
so, S = 0 + 1/2 × 10 × 4²
= 1/2 × 10 × 16
= 80 m

hence, height of building is 80m.

[note :- here I assumed acceleration due to gravity, g = 10m/s² ]