Question

An object is projected from point A with velocity u at an angle alpha with horizontal. In its parabloic path ,at point p the particle is moving at right angles to its initial direction of projection. Its velocity at p is

Answer 1

Initial velocity = u = u cos α i + u sin α j
velocity at p = v = v cos β  i + v sin β j,    where β = α - π/2
                          = v sin α i - v cos α j

We know  u cos α = horizontal component remains the same.
       u cos α = v sin α    =>  v = u cot α
    The angle of the velocity is :  β = α - π/2

Answer 2

see attachment.......