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Question
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Solution
The physical quantity is ‘torque’.
Torque may be defined as the turning effect produced by a force on a rigid body about a point, pivot, or fulcrum. It is measured by the product of force and the perpendicular distance of the pivot from the line of action of force.
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RELATED QUESTIONS
The S.I. unit of force is kgf. (kilogram-force)
Match the column
| Column A | Column B |
| (a) Camel | (1) broad and deep foundation |
| (b) Truck | (2) broad feet |
| (c) Knife | (3) six or eight tyres |
| (d) High building | (4) sharp cutting edge |
| (e) Thrust | (5) atm |
| (f) Moment of force | (6) N |
| (g) Atmospheric pressure | (7) N m |
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.

- Which force has the least moment about O? Give a reason.
- Which force has the greatest moment about O? Give a reason.
- Name the forces producing
(a) Clockwise
(b) anticlockwise moments. - What is the resultant torque about the point O?
Give two examples of a couple's actions in our daily life.
A nut is opened by a wrench of length 10 cm. if the least force required is 5.0 N. find the moment of force needed to turn the nut.
A wheel of diameter 2 m is shown in the figure with the axle at O. A force F = 2 N is applied at B in the direction shown in the figure. Calculate the moment of force about
- the centre O, and
- the point A.

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

A wheel of diameter 3 m is shown in fig. 2 with axle at 0. A force F = 8 N is applied at Q in the direction shown in figure. Calculate the moment of force about:
(i) centre o, and
(ii) point p.

Fig. 5 shows a uniform meter scale weighing 200 gf. Provided at its centre. Two weights 300 gf and 500 gf are suspended from the ruler as shown in the diagram. Calculate the resultant torque of the ruler and hence calculate the distance from mid-point where a 100 gf should be suspended to balance the meter scale.

A couple of 15 N force acts on a rigid body, such that arm of couple is 85 cm. Calculate moment of couple in the SI system.
