Question

The diagram shows two forces F₁ = 5 N and F₂ = 3N acting at point A and B of a rod pivoted at a point O, such that OA = 2m and OB = 4m

Calculate:

1. Moment of force F₁ about O
2. Moment of force F₂ about O
3. Total moment of the two forces about O.

Answer 1

Given AO = 2m and OB = 4m

1) Moment of Force F₁ (= 5N) at A about the point O

= F₁ × OA

= 5 × 2

= 10 Nm (anticlockwise)

2) Moment of force F₂ = (= 3N) at B about the point O

= F₂ × OB

= 3 × 4

= 12 Nm (clockwise)

3) Total moment of forces at O

= clockwise moments - anticlockwise moments

= 12 - 10

= 2 Nm (clockwise)