Question

Two equal opposite forces act on a rigid body . under what conditions will the body . 1) rotate 2) will not rotate

Answer 1

(a) Two equal and opposite forces acting on a rigid body such that their lines of action don't coincide constitute a couple. This couple produces the turning effect on the body. Hence, the rigid body will rotate.
(b)If the two equal and opposite forces act in such a way that their lines of action coincide, then the body will not rotate.

Answer 2

Explanation:

if two forces line of contact don't coincide = body rotate

if two forces line of contact coincide = body not rotate.