A ball is projected perpendicularly from an inclined plane of angle `theta`, with speed 'u' as shown. The time after which the projectile is making angle `45^(@)` with the inclined plane is :

Options

A. `(u)/(g sin theta)`
B. `(u)/(g cos theta)`
C. `(u)/(g{sin theta+cos theta})`
D. `(u)/(g{sin theta - cos theta})`

Answer

C

Explanation

A ball is ……..
`V_(y) = u-g cos theta t`
`V_(x) = g sin theta t`
`tan alpha = (V_(y))/(V_(x))`
`tan45^(@) = (u-gt cos theta)/(gt sin theta)`
`t =(u)/(g{sin theta+cos theta})` .