A ball is projected horizontally with a speed `u` from the top of inclined plane of inclination `alpha` with horizontal. At what distance along the plane, the ball will strike the plane ?

Explanation

Let the ball strikes the plane at th point `A`.
`OA = d = ?`
Using the equation of trajectory, we get
`y = (gx^(2))/(2u^(2))`
`(y)/(x) = (gx)/(2u^(2))`
`tan alpha = (g)/(2u^(2)) (d cos alpha)`
`d = (2u^(2))/(g)tan alpha sec alpha`