Question

Two forces each of magnitude $10N$ act vertically upwards and downwards respectively at the two ends of a uniform rod of length $4m$ which is pivoted at its mid point as shown in Fig. Determine the magnitude of resultant moment of forces about the pivot $O$.

• A. $2.5N$ $m$ (clockwise)
• B. $2.5N$ $m$ (anti clockwise)
• C. $40N$ $m$ (clockwise)
• D. $40N$ $m$ (anti clockwise)

Answer 1

Answer: (C)

$40N$ $m$ (clockwise)

Magnitude of force applied on each end = $10N$ .

The moment of force $\tau =r\times F$. Hence in bothe the cases, moment of force is in the clockwise direction, and the moment of forces add to one another.

The magnitude of $\tau =2\times 10\times 2=40Nm$ in the clockwise direction.