Question

The figure shows a bar AB pointed in the middle at point O. Two forces, 15 N each, act on this bar at ends A and B in the opposite direction. What is the magnitude of the resultant moment of force about point O?

Answer 1

Given Data:

Force at end A (F₁) = 15 N (Upward)

Force at end B (F₂) = 15 N (Downward)

Total arm length (AB) = 4 m

Pivot point O is in the middle, so distance is:

OA = `4/2` = 2 m

OB = `4/2` = 2 m

Calculation:

Both forces rotate the bar in the same clockwise direction about point O.

Resultant Moment about O = Moment due to F₁ + Moment due to F₂

= (F₁ × OA) + (F₂ × OB)

= (15 × 2) + (15 × 2)

= 30 + 30

= 60 N.m

The magnitude of the resultant moment of force about O is 60 N.m.