A wedge of mass `M` resting on a horizontal frictionless surface is acted upon by a force `F` in the horizontal direction as shown in figure. Find the net horizontal force acting on the shaded portion of the wedge.

Explanation

The net force is always equal to mass `x` acceleration Newton's `2^(nd)` Law.
`F_(shaded)=M_(shaded)A=(M)/(3)A`
`A=(F)/(M)`
`F_(shaded)=F//3`.