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A boy weighing 40 kgf climbs up a stair of 30 steps each 20 cm high in 4 minutes and a girl weighing 30 kgf does the same in 3 minutes. Compare:
- The work done by them.
- The power developed by them.
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State the characteristics required in a material to be used as an effective fuse wire.
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A stone of mass m is rotated in a circular path with a uniform speed by tying a strong string with the help of your hand. Answer the following questions
1) Is the stone moving with a uniform or variable speed?
2) Is the stone moving with a uniform acceleration? In which direction does the acceleration act?
3) What kind of force acts on the hand and state its direction?
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When a body is placed on a table top, it exerts a force equal to its weight downwards on the table top but does not move or fall

1) Name the force exerted by the table top
2) What is the direction of the force?
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In a beam balance, when the beam is balanced in a horizontal position, it is in ______ equilibrium.
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How is work done by a force measured when the force is in the direction of displacement?
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Give the expression for mechanical advantage of an inclined plane in terms of the length of an inclined plane.
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For a fuse, higher the current rating ________ is the fuse wire.
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Name the high energetic invisible electromagnetic waves which help in the study of the structure of crystals
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State an additional use of the X-rays waves
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Draw a simplified diagram of a lemon crusher, indicting of load and effort
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When does a force do work?
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A man having a box on his head, climbs up a slope and another man having an identical box walks the same distance on a levelled road.
Who does more work against the force of gravity and why?
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A wave has wavelength 50 Å.
- Name the wave.
- State its speed in vacuum.
- State its one use.
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Two copper wires are of the same length, but one is thicker than the other. Which wire will have more resistance?
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How is the unit horsepower related to the S.I. unit of power?
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A fuse is rated 8A. Can it be used with an electrical appliance rated 5 KW, 200 V ? Give a reason.
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What do you mean by an equilibrium of a body?
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State the condition when a body is in static equilibrium.
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