At t = 2 sec, a projectile is moving upwards. Its speed is 20 m/s and it is making at angle `30^(@)` with horizontal. What is angle of projection of the projectile from ground ?

Options

A. `tan^(-1)(2)`
B. `45^(@)`
C. `60^(@)`
D. `tan^(-1) (3)`

Answer

C

Explanation

`u cos theta = 20 cos 30^(@)`
`u cos theta = (20 sqrt3)/(2) = 10 sqrt3 m//s`
`v_(y) = u_(y) + a_(y) t`
`20 sin 30^(@) = u sin theta - g xx 2`
`u sin theta = 30 m//s`
`tan theta = (u_(y))/(u_(x)) = (u sin theta)/(u cos theta)`