A shell of mass 2 m fired with speed u at an angle to the horizontal explodes at the highest point of its motion into two fragments of mass m each. If one fragment, whose initial speed is zero, falls vertically, .the distance at which the other fragment falls from the gun is given by
Momentum of the shell at highest point
As one fragment has initial speed zero (stationary) and hence the other fragment of mass m has velocity component in horizontal direction. This will move under gravity. So it wilt fall at a distance which is equal to range.
Hence, distance covered from the gun