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An electric motor of power 100 W is used to drive the stirrer in a water bath. If 50% of the energy supplied to the motor is spent in stirring the water. Calculate the work done on the water in one minute.
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The weights of two bodies are 2.0 N and 2.0 kgf respectively what is the mass of each body?
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A girl of mass 40 kg runs a height of 80 stairs, each 25 cm high with a load of 20 kg on her head in 25 sec. If g is 10 m/s2, find:
(i) Gravitational force acting on the girl.
(ii) Work done by her.
(iii) Useful work done by her.
(iv) Her power in watt.
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A water pump raises 50 kg of water through a height of 25 m in 5s. Calculate the power supplied by the pump (Take: g = 10 N kg−1).
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An electric motor pump is 60% efficient and is rated 2.5 H.P. Calculate the maximum load it can lift through a height of 10m in 8 sec. (1 H.P. = 750 W).
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Name a machine which can be used to multiply force and change the direction of force applied.
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Light of different colours is deviated through different angles by a prism. Explain the reason.
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Give a reason, why the violet colour of white light deviated most and red colour of white light deviated least.
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What is understood by the term dispersion of light? What is its cause?
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Name the radiation of a wavelength longer than 8 × 10−7 m.
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Explain, why quartz prism is required for obtaining the spectrum of ultra-violet light?
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A prism causes dispersion of white light while a rectangular glass block does not. Explain.
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Draw a neat diagram to show the arrangement you would use to project a pure spectrum of white light on a screen.
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Comment on the statement: ‘When any ray of white light is incident on a glass prism, it simply disperses it into its seven constituent colours.
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What is sound? What causes it to produce?
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Arrange the speeds of sound in gases, solids, and liquids in ascending order.
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The speed of sound is more in hydrogen than in nitrogen. Is this statement true? Give a reason for your answer.
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