What is the formula for Torque acting due to couple (or) Moment of couple ?

Two equal and opposite parallel forces acting at different points in a body constitute a couple. Pedals of bicycles is the example for couple, where the two forces are equal but acting in opposite direction.

Torque acting due to couple (or) Moment of couple Torque is calculated by the product of either of forces forming the couple and the arm of the couple.

Torque = one of the force × perpendicular distance between the forces.

In the figure, two equal forces F and F acting on the arm LM. Let us consider O as the mid-point of the arm .The forces F and F, which constitute a couple, are acting in opposite direction.

From the figure, the formula or equation for Principle of moments is given as,

Moment of couple or torque = F × LM.

The moment becomes zero when the forces acting on the body have the same line of action. When the forces are at right angles to the arm (θ=90⁰), the torque is maximum.