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 case normal rection will pass through `O`. The cube will tip about `O` if torque of `F` exceeds the torque of mg.

Hence, `F((3a)/4)gtmg(a/2)` or `Fgt2/3mg`
Therefore, minimum value of `F` is `2mg//3`