A boy of mass 25 kg stands on a board of mass 10 kg which in turn is kept on a frictionless horizontal ice surface. The boy makes a jump with a velocity component 5m/s in a horizontal direction with respect to the ice. With what velocity does the board recoil? With what rate are the boy and the board seperate from each other?

Explanation

Consider the board boy as a system. The exterN/Al forces on this system are a. weight of the system and b. normal contact force by the ice surface. Both these force are vertical and there is no exterN/Al force in horizontal directio. The horizontal component of linear momentum of the board+boy system is therefore constant.
If the board redcoils at a speed v
`0=(25kg)xx(5m/s)-(10kg)v`
or, `v=12.5m/s`
The boy and the board are separating wilth a rate
`5m/s+12.5m/s=17.5m/s`