. Figure 1.31 shows two forces each of magnitude 10 N acting at the points A and B


Figure 1.31 shows two forces each of magnitude 10 N 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.

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Best Answer

(i)Perpendicular distance of point A from the force F=10 N at B is 0.5 m, while it is zero from the force F=10 N at A

Hence, moment of force about A is

= 10 N x 0.5 m=5 Nm(clockwise)

(ii)Perpendicular distance of point B from the force F=10 N at A is 0.5 m, while it is zero from the force F=10N at B

Hence, moment of force about B is

= 10 N x 0.5m =5 Nm(clockwise)

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

Moment of force F(=10 N) at A about O= 10N x 0.25 m

=2.5Nm(clockwise)

And moment of force F(=10N) at B about O

=10N x 0.25m=2.5Nm(clockwise)

Hence, total moment of the two forces about O

=0.25 + 0.25=5Nm (clockwise)

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