Consider a freely rotating body which is fixed at a point.
Consider a force F acting on a body. This force will rotate the body about the fixed point, as long as the line of action of the force passes through O which is a fixed point. This rotating tendency or the turning effect of the force about that point is called moment of force. In other words, the turning effect of the force acting on a body about an axis or point is called moment of force. We can also say that Moment of force is equal to the product of the magnitude of the force and the perpendicular distance of the line of action of the force from the axis of rotation.
Therefore the formula for moment of force is given as,
Moment of force about the point O = Force × perpendicular distance of the force from the Point O
Moment of force about the point O = F × ON
The unit of moment of force is N m and the dimensional formula is ML2T2