If a ball is thrown up with a velocity v from the top of a building the ball reaches the ground with a velocity 3u. Find the height of the building.

Options

A. `9 u^2//g`
B. `6 u^2//g`
C. `4 u^2//g`
D. `3u^2//g`

Answer

C

Explanation

`v^2 = u^2 + 2as`
`(3u)^2 = (u)^2 + 2 xx g xx h`
`implies 9 u^2 = u^2 + 2gh`
`implies h = (4u^2)/g`