Question

a stone is dropped from the edge of the roof. it passes a window 2m high in 0.1 sec. how far is the roof above the top of the window

Answer 1

Answer:

19.0125 m.

Explanation:

let H 1 be the distance of the roof above the top of the window

and H 2 be the distance of the roof above the bottom of the window

H 2 = gt2²/2

H 1 = gt1²/2

H 2 - H 1 = g/2 ( t2² - t1² ) = 5  ( t2² - t1² )  = 2

2 = 5( t2² - t1² )  = 5( t2² - t1² ) = 5 ( t2 - t1 ) ( t2 + t1 )

2 = 5 (0.1) ( t2+ t1 ) = 0.5 ( t2 + t1 )

t2 + t1 = 4

t2 - t1 = 0.1

2t1 = 3.9 , t1 = 3.9/2 = 1.95 s

therefore

H1 = 5(1.95)² = 19.0125 m.