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When two surfaces are polished, the friction coefficient between them decreases. But the friction coefficient increases and becomes very large if the surfaces are made highly smooth. Explain.
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While walking on ice, one should take small steps to avoid slipping. This is because smaller steps ensure
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Consider the situation shown in figure. The wall smooth but the surface of A and B in contact are rough. The friction on B due to A in equilibrium
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A heavy box is kept on a smooth inclined plane and is pushed up by a force F acting parallel to the plane. Does the work done by the force F as the box goes from A to B depend on how fast the box was moving at A and B? Does the work by the force of gravity depend on this?
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Suppose all the surface in the previous problem are rough. The direction of friction of B due to A
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A spring-mass system oscillates with a frequency v. If it is taken in an elevator slowly accelerating upward, the frequency will
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A spring-mass system oscillates with a car. If the car accelerates on a horizontal road, the frequency of oscillation will
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A piece of wood is taken deep inside a long column of water and released. It will move up
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A solid sphere falls with a terminal velocity of 20 m s−1 in air. If it is allowed to fall in vacuum,
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A solid sphere moves at a terminal velocity of 20 m s−1 in air at a place where g = 9.8 m s−2. The sphere is taken in a gravity-free hall having air at the same pressure and pushed down at a speed of 20 m s−1.
(a) Its initial acceleration will be 9.8 m s−2 downward.
(b) It initial acceleration will be 9.8 m s−2 upward.
(c) The magnitude of acceleration will decrease as the time passes.
(d) It will eventually stop
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Which of the following gases has maximum rms speed at a given temperature?
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Suppose a container is evacuated to leave just one molecule of a gas in it. Let va and vrms represent the average speed and the rms speed of the gas.
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The rms speed of oxygen at room temperature is about 500 m/s. The rms speed of hydrogen at the same temperature is about
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The rms speed of oxygen molecules in a gas is v. If the temperature is doubled and the oxygen molecules dissociate into oxygen atoms, the rms speed will become
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Find the rms speed of hydrogen molecules in a sample of hydrogen gas at 300 K. Find the temperature at which the rms speed is double the speed calculated in the previous part.
Use R=8.314 JK-1 mol-1
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What should be the condition for the efficiency of a Carnot engine to be equal to 1?
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The heat current is written as `(ΔQ)/(Δt)`. Why don't we write `(dQ)/dt?`
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Does a body at 20°C radiate in a room, where the room temperature is 30°C? If yes, why does its temperature not fall further?
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The thermal radiation emitted by a body is proportional to Tn where T is its absolute temperature. The value of n is exactly 4 for
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A blackbody does not
(a) emit radiation
(b) absorb radiation
(c) reflect radiation
(d) refract radiation
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