A, B and C are the three forces each of magnitude 4 n acting in the plane of the paper as shown in Figure. The point O lies in the same plane.
1) Which force has the least moment about O? Give a reason.
2) which force has the greatest moment about O? Give a reason.
3) Name the forces producing (a) Clockwise (b) anticlockwise moments.
4) what is the resultant torque about the point O?
1) We know that
Moment of Force = Force x Perpendicular distance
Since the perpendicular distance of vector C is least from the point O.
Vector C will have the least moment about O.
2) We know that
Moment of force = Force x Perpendicular distance
Since the perpendicular distance of vector A is greatest from the point O.
Vector A will have the greatest moment about O.
3.a) Vector A and B will produce clockwise moments.
Explanation: if the turning effect on the body is clockwise.
The moment if force is called clockwise moment and it is taken as negative.
3.b) Vector C will produce anticlockwise moment.
Explanation L if the turning effect on the body is anticlockwise.
Moment of force is called anticlockwise moment and it is taken as positive.
4) Resultant torque about point O = sum of torques due to vectors A, B, and C
∴Resultant torque about point O.
`= -(4 xx 0.9) - (4 xx 0.8) + (4 xx 0.6) Nm`
= -3.6 - 3.2 + 2.4
= -4.4 Nm
The negative sign suggests that the resultant torque is in the clockwise direction.