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प्रश्न
State when the moment of force is positive and when it is negative.
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उत्तर
If the couple has a tendency to rotate the body in an anti-clockwise direction then its moment is taken positive and if the tendency of rotation is clockwise then the moment is negative.
संबंधित प्रश्न
State two effects of a force when applied on a body.
How does the effect of force differ when it is applied on a non-rigid body?
Name of S.I. unit of the rate of change in momentum.
State Newton's third law of motion.
Name and define the S.I. and C.G.S. units of force. How are they related?
Classify the following amongst contact and non-contact forces.
magnetic force
Fig. shows a uniform meter scale weighing 100 N pivoted at its centre. Two weights of 500 N and 300 N are hung from the ruler as shown in fig.
(i) Calculate total clockwise and anticlockwise moments.
(ii) Calculate difference in clockwise moment and anticlockwise moment.
(iii) Calculate the distance from O where a 100 N weight should be suspended to balance the meter scale.
Assertion & Reasoning
- Assertion: The sum of the clockwise moments is equal to the sum of the anticlockwise moments.
- Reason: The principle of conservation of momentum is valid if the external force on the system is zero.
The diagram shows wheel O pivoted at point A. Three equal forces F1, F2 and F3 act at point B on the wheel.
- Which force will produce maximum moment about A?
- Give a reason for your answer in (a).
A person standing in front of a cliff fires a gun and hears its echo after 3 s. If the speed of sound in air is 336 ms−1.
- Calculate the distance of the person from the cliff.
- After moving a certain distance from the cliff, he fires the gun again, and this time the echo is heard 1.5 s later than the first. Calculate the distance that the person moved.
