A boy standing at the top of a tower of 20m of height drops a stone. Assuming `g=10ms^(-2)`, the velocity with which it hits the ground is :-

Options

A. `10.0m//s`
B. `20.0m//s`
C. `40.0m//s`
D. `5.0m//s`

Answer

b

Explanation

`h=20m,u=0`
ball hit the ground with velocity v
`therefore v^(2)=u^(2)+2gh`
`v^(2)=0+2xx10xx20`
`v=20m//s`