A body is projected with horizontal with a velocity 20 m/s from top of the tower. It touches the ground at angle ‘α’ with velocity of 40 m/sec. Value of  α is

Horizontal component of velocity is constant through out the motion given initial velocity u= ux=20 m/s final velocity =v=40 m/s   ux=vx 20=v cosα 20=40 Cos α ⇒12=Cos α cos600=Cos α ⇒α=600