# Classification of Couple in Engineering Mechanics

## Couple in Engineering Mechanics:

A couple is a pair of forces applied to the key of a lock.

## Arm of a Couple:

The perpendicular distance (a) between the lines of action of the two equal and opposite parallel forces is known as the Arm of a couple.

## Moment of a Couple:

The moment of a couple is the product of the force (i.e, one of the forces of the two equal and opposite parallel forces) and the arm of the couple. Mathematically,

Moment of a couple = P x a
where,

P = Magnitude of the force and
a = Arm of the couple

## Classification of Couple:

The couples may be broadly classified into the following two categories, depending upon their direction, in which the couple tends to rotate the body on which it acts:

• Clockwise Couple
• Anticlockwise Couple

### Clockwise Couple:

A couple whose tendency is to rotate the body, on which it acts in a clockwise direction is known as a clockwise couple. Such a couple is also called a positive couple.

### Anticlockwise Couple:

A couple whose tendency is to rotate the body, on which it acts, in an anticlockwise direction is known as an Anticlockwise couple. Such a couple is also called a negative couple.