UPSC  Physics

81. If the radius of the earth were to shrink by one per cent, its mass remaining the same, the value of g on the earth’s surface would:

increase by 0.5% increase by 2% decrease by 0.5% decrease by 2%

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82. Which one of the following is the correct sequence of the given substances in the decreasing order of their densities?

Steel > Mercury > Gold Gold > Mercury > Steel Steel > Gold > Mercury Gold > Steel > Mercury

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83. Four wires of same material and of dimensions as under are stretched by a load of same magnitude separately. Which one of them will be elongated maximum?

Wire of 1m length and 2 mm diameter Wire of 2 m length and 2 mm diameter Wire of 3 m length and 1.5 mm diameter Wire of 1 m length and 1 mm diameter

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84. Three identical vessels A, B and C are filled with water, mercury and kerosene respectively up to an equal height. The three vessels are provided with identical taps at the bottom of the vessels. If the three taps are opened simultaneously, then which vessel is emptied first?

Vessel B All the vessels A, B and C will be emptied simultaneously Vessel A Vessel C

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85. Consider the following statements:
If there were no phenomenon of capillarity
1. it would be difficult to use a kerosene lamp
2. one would not be able to use a straw to consume a soft drink
3. the blotting paper would fail to function
4. the big trees that we see around would not have grown on the Earth
Which of the statements given above are correct?

1, 2 and 3 only 1, 3 and 4 only 2 and 4 only 1, 2, 3 and 4

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86. Ball bearings are used in bicycles, cars, etc., because

the actual area of contact between the wheel and axle is increased the effective area of contact between the wheel and axle is increased the effective area of contact between the wheel and axle is reduced None of the above statements is correct

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87. Consider the following statements:
1. A geo-stationary satellite is at an approximate height of 10,000 km.
2. FM transmission of music is of very good quality because the atmospheric or man made noises which are generally frequency variations can do little harm.
Which of the statements give above is/are correct?

1 only 2 only Both 1 and 2. Neither 1 nor 2

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88. Assertion (A): A piece of copper and a piece of glass are heated to the same temperature. When touched, thereafter, the copper piece appears hotter than the glass piece.
Reason (R): The density of copper is more than that of glass.

Both A and R are true and R is the correct explanation of A Both A and R are true but R is not a correct explanation of A A is true but R is false A is false but R is true

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89. A hollow sphere of radius R, a hollow cube of side R and a thin circular plate of radius R, made up of the same material, are all heated to 20°C above room temperature. When left to cool in the room, which of them will reach the room temperature first?

Circular plate Cube Sphere All of them will reach the room temperature at the same time

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90. Consider the following statements:
1. Steam at 100°C and boiling water at 100°C contain same amount of heat.
2. Latent heat of fusion of ice is equal to the latent heat of vaporization of water.
3. In an air-conditioner, heat is extracted from the room air at the evaporator coils and is rejected out at the condenser coils.
Which of these statements is/are correct?

1 and 2 2 and 3 Only 2 Only 3

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