Question

A body released from the top of a tower falls through half the height of tower in `3` seconds. If will reach the ground after nearly .
A. (a) ` 3 . 5 sec `
B. (b) ` ` 4 . 24 sec`
C. (c )` 4. 71 sec`
D. (d)` 6 sec`

Answer 1

Correct Answer - B
Let (h) be the total height of tower , tower , taking fall of the body in ` 3 s, u=0`
` S =h/2 , = g = 9.8 m//s^2 , t=3 sec` ,bRgt or ` S =ut + 1/2 at^2 :. h/2 =0 xx 3 = 1/2 xx (9.8) (3)^2`
or ` h=9.8 xx 9 m` ltbRgt Now, if body takes total tiem (t) to fall therough height (h) , then
` h= 1/2 xx 9.8 xx t^2 ` or t= =sqrt (2 h)/(9.8)`
or ` t= sqrt ((2 xx 9.0 xx 9 )/(9.8) = 3 sqrt 2 sec = 4 . 24 sexs`.