**Moment of Force**

Sometimes, a force can cause an object to rotate. For example, when a force is applied to the end of a spanner, a turning effect will be produced, which helps to screw or unscrew a nut.

**The turning effect produced by force is called a moment**. The magnitude of moment can be calculated by multiplying the magnitude of the force by the perpendicular distance from the pivot.

**Moment = F x d**

Moment (N·m)

F = force (N)

d = perpendicular distance between force and pivot (m)

*Describe how the lever-arm is used to move the bolt, and suggest why the spring is needed.*

- If you push the lever-arm to the left, the bolt will move to the left. The spring is needed to return the lever-arm to the right.

*The force applied at point B is 22 N. The pivot is 110 cm from point B and 38 cm from point A. Calculate the force exerted on the lever-arm at point A by the spring. *

- The moment caused by the force applied at B with respect to the pivot is equal to the moment caused by the force at A with respect to the pivot.

(22 N) x (110 cm) = F_{A} x (38 cm)

F_{A} = (22 N) x (110 cm) / (38 cm) = 64 N

*Explain how the force applied at point B would need to change if the distance from the pivot to point A is increased.*

- Since the distance to from the pivot to A increased, the moment will also have increased.

- The distance from the pivot to B remains constant.

- For the moment to have increased while the distance remains constant, the force applied at point B should have increased.