A body dropped from top of a tower falls through ` 40 m` during the last two seconds of its fall. The height of tower in m is ( g= 10 m//s^2)`

Options

A. 60
B. 45
C. 80
D. 50

Answer

B

Explanation

Let height of minaret be H body take time T to fall from top to bottom.

`H=(1)/(2)gT^(2)` …..(i)
In last 2 s body travels distance of 40 m so in (T - 2) second distance travelled = (H - 40)m
`(H-40)=(1)/(2)g(T-2)^(2)`
By solving Eqs. (i) and (ii), T = 3 s and H = 45 m