Two balls are dropped to the ground from different heights. One ball is dropped 2s after the other but they both strike the ground at the same time. If the first ball takes 5 s to reach the ground, then the difference in initial heights is `(g=10ms^(-2))`

Options

A. 20 m
B. 80 m
C. 170 m
D. 40 m

Answer

B

Explanation

`s_(1)=(1)/(2)g t_(1)^(2)=(10)/(2)xx(5)^(2)=125m`
`s_(2)=(1)/(2)g t_(2)^(2)=(10)/(2)xx(3)^(2)=45m`
`therefore s_(1)-s_(2)=125-45=80m`