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 that is directly above the centre of the face, at a height 3a/4 above the base. The minimum value of F which the cube begins to tip about the edge is ....(Assume that the cube does not slide).

Options

A. `(Mg)/3`
B. `2/3 mg`
C. `Mg`
D. `(Mg)/(sqrt(2))`

Answer

B

Explanation

Talking moments about of point O

Moment of N (normal reaction) and f (force of friction) are zero. In critical case normal reaction will pass through O. the tip about the edge, moment of F should be greater than moment of mg or, `F=((3a)/4) gt (mg)a/2`
`F gt 2/3 mg`