Three forces acting on a rigid body are represented in magnitude, direction and line of action by the three sides of a triangle taken in order. The forces are equivalent to a couple whose moment is equal to twice the area of the triangle.

Three forces acting on a rigid body are represented in magnitude, direction and line of action by the three sides of a triangle taken in order. The forces are equivalent to a couple whose moment is equal to twice the area of the triangle.

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The principle of transmissibility of forces states that, when a force acts upon a body, its effect is minimum, if it acts at the centre of gravity of the body.

A smooth cylinder lying on a horizontal surface is in neutral equilibrium

A couple produces rotational motion.

The algebraic sum of the forces, constituting the couple is zero.

The algebraic sum of the forces, constituting the couple, about any point is the same.

A couple cannon be balanced by a single force but can be balanced only by a couple of opposite sense.