An aeroplane moves with a horizontal velocity U at a height h. It drops a bomb. Then the time taken by the bomb in reaching the ground will be equal to

bomb velocity has, initial velocity horizontal component=ux=velocity of aeroplane initial velocity vertical component=uy=0 apply in sy=uyt+12gt2   here  sy=height of plane from ground=h; substitute in the equation, h=12gt2 t=2hg