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The MCQs below are drawn from the Physics subject category.
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31
A piece of ice having a stone frozen in it floats in a glass vessel filled with water. How will the level of water in the vessel change when the ice melts?
A. the vessel will break
B. the level will drop
C. the level will rise
D. the level will not change
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Correct Option
Explanation
When the ice melts the stone sinks and displaces only its own volume (less than when part of the ice), so the water level falls.
32
6. A common hydrometer reads specific gravity of liquids. Compared to 1.6 on the stem, the mark 1.5 will be
A. may be upward or downward depending upon the hydrometer
B. upward
C. in the same place
D. downward
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Correct Option
Explanation
A lower specific gravity makes the hydrometer sink deeper, so the 1.5 mark (lower SG) will lie lower on the stem compared to the 1.6 mark.
33
A material has normal density p and bulk modulus K. The increase in the density of the material when it is subjected to an external pressure P from all sides is
A. pP/K
B. pK/P
C. K/pP
D. P/pK
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Correct Option
Explanation
Volume fractional change = -ΔP/K, so density change Δρ/ρ = -ΔV/V = ΔP/K, hence Δρ = ρ P / K (pP/K).
34
100. De Broglie hypothesized that the linear momentum and wavelength of a free massive particle are related by which of the following constants?
A. Planck's constant
B. The speed of light
C. Boltzmann's constant
D. The Rydberg constant
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Correct Option
Explanation
De Broglie's relation is p = h/λ, using Planck's constant h.
35
J-second can be written in terms of base units as:
A. kg^2·m^-1·s^2
B. kg·m·s^2
C. kg·m^2·s^-1
D. kg·m^2·s^-3
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Correct Option
Explanation
A joule-second is (kg·m^2·s^-2)·s = kg·m^2·s^-1, so option A is correct.
36
Unit for measuring intensity of light is:
A. Mole
B. Candela
C. Decibel
D. Steradian
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Correct Option
Explanation
The SI unit of luminous intensity is the candela.
37
Which of the following does not have the same units:
A. Heat
B. Work
C. Power
D. Kinetic energy
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Correct Option
Explanation
Work, heat and kinetic energy have units of energy (joules), whereas power has units of energy per time (watts).
38
Pressure applied to enclosed fluid is
A. diminished and transmitted to wall of container.
B. Increased in proportion to the mass of the fluid and then transmitted.
C. transmitted unchanged to every portion of the fluid and walls of containing vessel.
D. Increased and applied to every part of the fluid,
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Correct Option
Explanation
Pascal's principle states that pressure applied to an enclosed fluid is transmitted unchanged to every part of the fluid and the walls.
39
An ornament made of silver is suspected to be hollow. It weighs 288.75 gm in air. It can displace 30 cc of water. If the specific gravity of silver is 10.5, the volume of cavity is
A. 2.50 cc
B. 7.5 cc
C. 5.00 cc
D. 3.00 cc
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Correct Option
Explanation
Volume of silver = mass / density = 288.75 / 10.5 = 27.5 cc; cavity = displaced volume − material volume = 30 − 27.5 = 2.5 cc.
40
A body floats in a liquid contained in a beaker. The whole system is shown in figure. The upthrust on the body due to liquid is
A. zero
B. equal to the weight of the immersed portion of the body
C. equal to the weight of the body in air
D. equal to the weight of liquid displaced
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Correct Option
Explanation
Archimedes' principle: the upthrust equals the weight of the liquid displaced by the body.
