A body is acted upon by two forces each of magnitude F, but in opposite directions. State the effect of the forces if
(a) both forces act at the same point of the body.
(b) the two forces act at two different points of the body at a separation r.

(a) As two forces of same magnitude are acting on a body at the same point and they are in opposite direction so the resultant force will be zero.

F – F = 0

(b) When two forces of same magnitude act on a body at two different points at a separation r and in opposite direction then the moment of force will be F × r

Moment of forces = F × r