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Why is fire hot?

Important Questions on Force, Work and Energy

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What are the limitations in harnessing wind energy?

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The capillary rise at  20°C in a clean glass tube of  1 mm bore containing water is approximately:
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Why is a ventilator provided in a room?
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A piece of wood having weight 5 kg floats in water with 60% of its volume under the liquid. The specific gravity of wood is:
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On absorbing heat the particles of matter :
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A ship whose hull length is 100 m is to travel at 10 m/sec. For dynamic similarity, at what velocity should a 1:25 model be towed through water?
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Why are chimneys provided over furnace in factories?
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Half portion of a rectangular piece of ice is wrapped with a white piece of cloth while the other half with a black one. In this context, which one among the following statements is correct?
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A piece of metal of specific gravity 7 floats in mercury of specific gravity 13.6 . What fraction of its volume is under mercury?
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The depth of the center of pressure on a vertical rectangular gate 8 m wide and 6 m high, when the water surface coincides with the top of the gate, is:
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The pressure in the air space above an oil (sp. gr. 0.8) surface in a tank is 0.1 kg/cm2. The pressure at 2.5 m below the oil surface will be:
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Heat transfers from
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A model of a reservior is drained in 4 minutes by opening the sluice gate. The model scale is 1: 225. How long should it take to empty the prototype ?
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The figure shows a glass tumbler containing hot milk which is placed in a tub of cold water. State the direction in which heat will flow.
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Amit had two balls 'P' and 'Q'made of paraffin. The masses of balls 'P' and 'Q' are 1 kg and 2 kg, respectively. He immersed both the balls in a water bath containing hot water. He observed that ball 'P' melts faster than ball 'Q'. Why is that so?
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Which of the following statements is not correct?
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The following is true for an open cycle gas turbine having exhaust heat exchanger. Atmospheric air before entering the compressor is
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Two objects at the same temperature one smaller than the other, are placed together. In which direction will the heat be transferred? Give reason.
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Akshat's mother had to set curd. She added a small amount of curd to warm milk. The microbes present in the curd help in setting if this mixture is kept approximately between 35° C to 40° C. In colder regions, generally, the setting of curd becomes difficult. Suggest a way to set curd in such a situation.
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A square surface 3m × 3m lies in a vertical line in the water pipe at its upper edge at the water surface. The hydrostatic force on the square surface is: