## WORK EXAMPLE QUESTIONS

- a) What do you understand by the moment of a force?

b) The Turing effect or moment of a force depends on two factors. What are they?

c) What is the principle of moments? what other rule also applies if a system is in equilibrium?

d) A metre rule is pivoted at its midpoint M with a vertical force of 20N hanging from the distance 40cm from M. At what distance must a 30N force hang to balance the ruler horizontally?

e) A 65g three quarter metre rule is freely pivoted at the 30cm mark. Determine where a 50g mass should be hung so as to balance the rule horizontally.

### SOLUTION

a) The moment of a force is a measure of turning effect of the force about a particular point. It is defined as follows.

**Moment of a force about a point = Force X perpendicular distance from the point.**

b) -The size of the force

- The distance away of the force from the pivot or fulcrum.

c) When an object is in equilibrium, the sum of the anti-clock wise moments are about any point is equal to the sum of the clock wise moments about that point.

The other rule that applies if a body must be in equilibrium is that, the sum of the forces in one direction must equal the sum of forces in the opposite direction.