A body of mass `m` is projected horizontally with a velocity `v` from the top of a tower of height `h` and it reaches the ground at a distance `x` from the foot of the tower. If a second body of mass `2 m` is projected horizontally from the top of a tower of height `2 h`, it reaches the ground at a distance `2x` from the foot of the tower. The horizontal veloctiy of the second body is.