Figure shows two forces each of magnitude 10N acting at the points A and B at a separation of 50 cm, in opposite directions. Calculate the resultant moment of the two forces about the point (i) A, (ii) B and (iii) O, situated exactly at the middle of the two forces.

Given,
Force at A = 10N
Force at B = 10N
Distance between A and B = 50cm = 0.5m

(i) Resultant moment of two forces at point A is

$10 \times 0.5 = 5Nm \text{ clockwise} \\[0.5em]$

Therefore, resultant moment of two forces at point A is 5 Nm (clockwise)

(ii) Resultant moment of two forces at point B is

$10 \times 0.5 = 5Nm \text{ clockwise} \\[0.5em]$

Therefore, resultant moment of two forces at point B is 5 Nm (clockwise)

(iii) Perpendicular distance of point O from either of the forces F = 10N is 0.25 m

Moment of force F at point A about O

$10 \times 0.25 =2.5Nm \text{ clockwise} \\[0.5em]$

Moment of force F at point B about O

$10 \times 0.25 =2.5Nm \text{ clockwise} \\[0.5em]$

Resultant moment of two forces about o is

$2.5 + 2.5 = 5Nm \text{ clockwise} \\[0.5em]$

Therefore, Resultant moment of two forces about o is 5Nm (clockwise)