Eight equal drops of water are falling through air with a steady

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 Multiple Choice QuestionsMultiple Choice Questions

61.

The term liquid crystal refers to a state that is intermediate between

  • crystalline solid and amorphous liquid

  • crystalline solid and vapour

  • amorphous liquid and its vapour

  • a crystal immersed in a liquid


62.

Water rises in plant fibres due to

  • capillarity

  • viscosity

  • fluid pressure

  • osmosis


63.

The cylindrical tube of a spray pump has a cross-section of 8 cm2, one end of which has 40 fine holes each of area 10-8 m2. Ifthe liquid flows inside the tube with a speed of 0.15 m min-1 the speed with which the liquid is ejected through the holes is

  • 50 ms-1

  • 5 ms-1

  • 0.05 ms-1

  • 0.5 ms-1


64.

A body weighs 50 g in air and 40 g in water. How much would it weigh in a liquid of specific gravity 1.5 ?

  • 30 g

  • 35 g

  • 65 g

  • 45 g


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65.

Two solid pieces, one of steel and the other of aluminium when immersed completely in water have equal weights. When the solid pieces are weighed in air

  • the weight of aluminium is half the weight of steel

  • steel piece will weigh more

  • they have the same weight

  • aluminium piece will weigh more


66.

The colloidal solution in which both the dispersed phase and dispersion medium are liquids are called

  • emulsions

  • gels

  • foams

  • liquid crystals


67.

Horizontal tube of non-uniform corss-section has radii of 0.1 m and 0.05 m respectively at M and N. For a streamline flow ofl iquid the rate of liquid flow is

          

  • changing continuously with time

  • greater at M than at N

  • greater at N than at M

  • same at M and N


68.

Three liquids of equal masses are taken in three identical cubical vessels A, B and C. Their densities are ρA, ρB and ρC respectively but ρA < ρB < ρC . The force exerted by the liquid on the base of the cubical vessel is

  • maximum in vessel C

  • minimum in vessel C

  • the same in all the vessels

  • maximum in vessel A


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69.

Water is in streamline flows along a horizontal pipe with non-uniform cross-section. At a point in the pipe where the area of cross-section is 10 cm2, the velocity of wateris 1 ms-1 and the pressure is 2000 Pa. The pressure at another point where the cross-sectional area is 5 cm2 is

  • 4000 Pa

  • 2000 Pa

  • 1000 Pa

  • 500 Pa


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70.

Eight equal drops of water are falling through air with a steady velocity of 10 cm s-1. If the drops combine to form a single drop big in size, then the terminal velocity of this big drop is

  • 40 cms-1

  • 10 cms-1

  • 30 cms-1

  • 80 cms-1


A.

40 cms-1

Here,          v  r2   v1v2 = r1182/3 . r2      10v2 = 14        v2 = 40 cm/s


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