A uniform cube of side a and mass `m` rests on a rough horizontal table. A horizontal force `F` is applied normal to one of the faces at a point directly above the centre of the face, at a height `(3a)/(4)` above the base. What is the minimum value of `F` for which the cube begins to tip about an edge?

Explanation

In the limiting normal reaction will pass through O . The cube will topple about O if torque of F exceeds the torque of mg

`rArr ((3a)/4) gt mg(a/2) , rArr F gt 2/3 mg`
So , the minimum value of F is `2/3 ` mg