Question

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

Calculate:

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

Answer 1

1. Moment of force F₁ about O = Force × AO
   = 5N × 2m
   = 10 Nm (anticlockwise)
2. Moment of force F₂ at O = Force × BO
   = 3N × 4m
   = 12 Nm (clockwise)
3. Total moment of force at O
   = clockwise moments − anticlockwise moments
   = 12 Nm − 10 Nm
   = 2 Nm (clockwise)