A ball is thrown horizontally from the top of a tower and strikes the ground in `3 s` at an angle of `30^@` with the vertical.
(a) Find the height of the tower.
(b) Find the speed with which the body was projected.

Options

A. `45m` , ` 15 sqrt(2) m s^-1`
B. `45m` , ` 10 sqrt(3) m s^-1`
C. `30m` , ` 15 sqrt(3) m s^-1`
D. `15m` , ` 10 sqrt(3) m s^-1`

Answer

B

Explanation

`h = (1)/(2) 10 (3)^2 = 45 m`
`v cos 30^@ = 10 xx 3`
`rArr v = 20 sqrt(3) m s^-1`
`u = v sin 30^@`
=`20 sqrt(3) xx (1)/(2) = 10 sqrt(3) m s^-1`.
.