**Moment of Force –** The physical quantity that produces the turning effect on the body about an axis is called the moment of force or torque.

**Measurement of torque –** The moment of torque is equal to the product of the magnitude of the force and the perpendicular distance of the line of action of a force from the axis of rotation.

**Mathematical Expression:**

Moment of force = Force × perpendicular distance.

**Unit of moment of force :**

- In SI unit, unit of moment of force is ‘
*Newton metre*‘ (N m) - In CGS unit, unit of moment of force is ‘
*dyne cm*‘.

**Factors affecting the turning of a body :**

(i) The magnitude of the applied force, and

(ii) the perpendicular distance of the line of the force from the pivoted point.

**Types of moments**

**(i) Clockwise moment –** If the effect on the body is to turn it anticlockwise, moment of force is called the anticlockwise moment.

**(ii) Anticlockwise moment –** If the effect on the body is to turn it clockwise, moment of force is called the clockwise moment.

** Note – the anticlockwise moment is taken as positive and the clockwise moment is taken as negative.*

**Some common examples of moment of force **

(i) turning of the steering wheel,

(ii) opening of the door,

(iii) using of a spanner to tighten or loosen a nut.