Moment of couple:

Sol.: The moment of couple is the product of the force (that is one of the forces of two equal and opposite parallel forces) and the arm of couple.

Mathematically:

Moment of couple = F.d N-m or N-mm

• The moment of couple can be clockwise or anticlockwise.
• The effect of couple is unchanged if and only if

1. The couple is shifted to some other position.

2. The couple is rotated by an angle.

3. Any pair of force the rotation effect of which is the same replaces the couple.

4. Sum of the forces forming couple in any direction is zero.