Question

Study the diagram alongside carefully and calculate the resultant moment of force about (a) point P (b) point Q (c) about point R which is exactly in the middle of P and Q.

Answer 1

(a) Moment of force due to F₁ about P = F₁ × ⊥ distance

= 20 N × 0

= 0

Moment of force due to F₂ about P = F₂ × ⊥ distance

= \[20 \text{ N} \times \frac{20}{100} \text{ m}\]

= 4 Nm in CWD

∴ Resultant moment of force about P = 0 + 4 Nm = 4 Nm in CWD

(b) Moment of force due to F₁ about Q = F₁ × ⊥ distance

= \[20 \text{ N} \times \frac{20}{100} \text{ m}\]

= 4 Nm in CWD

Moment of force due to F₂ about Q = F₂ × ⊥ distance

= 20 N × 0

= 0

∴ Resultant moment of force about Q = 4 Nm + 0 = 4 Nm in CWD

(c) Moment of force due to F₁ about R = F₁ × ⊥ distance

= \[20 \text{ N} \times \frac{10}{100} \text{ m}\]

= 2 Nm in CWD

Moment of force due to F₂ about R = F₂ × ⊥ distance

= \[20 \text{ N} \times \frac{10}{100} \text{ m}\]

= 2 Nm in CWD

∴ Resultant moment of force about R = 2 Nm + 2 Nm

= 4 Nm in CWD