Please select a subject first
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A satellite revolves around the earth in a circular orbit. What is the work done by the force of gravity? Give reason.
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A coolie X Carrying a load on his head climbs up a slope and another coolie Y carrying the identical load on his head move the same distance on a frictionless horizontal platform. Who does more work? Explain the reason.
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The work done by a fielder when he takes a catch in a cricket match, is negative. Explain.
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Give an example when work done by the force of gravity acting on a body is zero even though the body gets displaced from its initial position.
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A light ray passes from water to
- air, and
- glass.
In each case, state how does the speed of light change.
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What are the S.I. and C.G.S units of work? How are they related? Establish the relationship.
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State and define the S.I. unit of work.
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What physical quantity does the electron volt (eV) measure? How is it related to the S.I. unit of that quality?
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How is kilowatt hour related to joule?
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State two factors on which power spent by a source depends. Explain your answer with examples.
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Differentiate between work and power.
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Name the quality which is measured in kWh.
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One horse power is equal to ______.
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kWh is the unit of ______.
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A body, when acted upon by a force of 10 kgf, gets displaced by 0.5 m. Calculate the work done by the force, when the displacement is (i) in the direction of force, (ii) at an angle of 60° with the force, and (iii) normal to the force. (g = 10 N kg-1)
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When light travels from a denser to a rarer medium, its speed ______.
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A boy weighing 350 N climbs up 30 steps, each 20 cm high in 1 minute, Calculate:
- the work done and
- power spent.
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A man spends 7.4 KJ energy in displacing a body by 74 m in the direction in which he applies force in 2.5 s. Calculate the force applied.
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An ox can apply a maximum force of 1000 N. It is taking part in a cart race and is able to pull the cart at a constant speed of 30 ms-1 while making its best effort. Calculate the power developed by the ox.
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The wavelengths for the light of red and blue colours are roughly 7.8 × `10^7` m and 4.8 × `10^7` m respectively.
(a) Which colour has the greater speed in vacuum?
(b) Which colour has the greater speed in glass?
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