Question

Two forces, each of magnitude 10 N, act vertically upwards and downwards respectively on the two ends of a uniform rod of length 4 m, freely pivoted at its midpoint as shown in Fig. Then the magnitude of the resultant moment of forces about the pivot O is.

Options

• 40 Nm (clockwise)

• 40 Nm (anticlockwise)

• 20 Nm (clockwise)

• 20 Nm (anticlockwise)

Answer 1

40 Nm (clockwise)

Explanation:

Length of rod = 4 m, so distance of each force from the pivot is:

`4/2 = 2 m`

Moment due to each force:

M = F × d

= 10 × 2

= 20 N m

Both forces produce a clockwise moment, so

`M_"resultant"`​ = 20 + 20

= 40 N m