A stone drops from the edge of the roof. It passes the window 2 m high in 0.1s . How far is the roof above the top of the window?
Solution)
Height of the window (h) = 2m
Acceleration due to gravity g = 9.8 m/s2
Time taken (t) = 0.1 s
The velocity of the stone when it reaches the top of the window is to be calculated.
Applying the II equation of motion,
h=ut+1/2 at^2
2=0.1u+0.049
0.1u=1.951
u= 19.51m/s
Thus, the velocity 19.51 m/s will be the final velocity of the stone when it is covering the distance between the roof and the window.
Initially the stone is at rest i.e., u = 0
v^2-u^2=2gh
(19.51)^2=19.6h
=> h= 19.42m
Distance between the roof and the window =19.42 m.