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One end of a spring is kept fixed while the other end is stretched by a force as shown in the diagram.

(i) Copy the diagram and mark on it the direction of the restoring force.
(ii) Name one instrument which works on the above principle.
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A boy of mass 30 kg is fitting at a distance of 2 m from the middle of a see-saw. Where should a boy of mass 40 kg sit so as to balance the see-saw?
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A ball is placed on a compressed spring. When the spring is released, the ball is observed to fly away.
(i) What form of energy does the compressed spring possess?
(ii) Why does the ball fly away?
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Give an experiment to verify the principle of moments.
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Derive a relation between the S.I. and C.G.S. unit of force.
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Calculate the work done when:
A car is moved on a rough road through 30 m against a frictional resistance of 75 N.
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A coolie carrying a load on his head and moving on a frictionless horizontal platform does no work. Explain the reason why.
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The world record for weight lifting was held by Sergei Didyk of the USSR. He lifted 261 kg to a height of 2.3 m in 4s; find:
(a) Weight lifted by him
(b) Work done by him
(c) Power developed by him. (g = 10m/s2)
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A machine raises a load of 750 N through a height of 16 m in 5 seconds. Calculate the power at which the machine works.
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State the C.G.S. unit of work. How it is related to its S.I. unit?
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A coolie carries a load of 30 kgf through a distance of 500 m in 5 minutes while another coolie B carries the same load through the same distance in 10 minutes. Compare the
(i) work done, and
(ii) power developed. (Take: g = 10md−2)
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A man weighing 700 N runs up a flight of 15 steps, each 20 cm high, in 5 seconds. Calculate the power of the man.
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A force of 1 kgf displaces a body by a distance of 10 cm
(i) in direction of force,
(ii) normal to the force
(iii) at an angle of 60° to the direction of the force.
Calculate the amount of work done in each case. (Take: g = 9.8 ms−2 )
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Why fuse wire must always be connected in ‘live’ wire? Explain.
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Where are the cartridge type fuse used?
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What is the rating of fuse used in light and fan circuits?
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What is the rating of fuse used in power circuits, in domestic use?
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What is an ‘electric fuse’? State its two characteristics of electric fuse.
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Explain the significance of kWh meter, main switch and main fuse in house-circuiting.
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