A hollow sphere of volume V is floating on water surface wit

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 Multiple Choice QuestionsMultiple Choice Questions

101.

The neck and bottom of a bottle are 3 cm and 15 cm in radius respectively. If the cork is pressed with a force 12 N in the neck of the bottle, then force exerted on the bottom of the bottle is

  • 30 N

  • 150 N

  • 300 N

  • 600 N


102.

A square wire frame of size L is dipped in a liquid. On taking out a membrane is formed. If the surface tension of liquid is T, then force acting on a frame will be

  • 2T L

  • 4T L

  • 8T L

  • 16T L


103.

64 spherical rain drops of equal size are falling vertically through air with a terminal velocity 1.5 ms-1 .If these drops coalesce to form a big spherical drop, then terminal velocity of big drop is

  • 8 ms-1

  • 16 ms-1

  • 24 ms-1

  • 32 ms-1


104.

The equation of a wave is y = 5 sin t0.04- x4 ; where x is in cm and t is in second. The maximum velocity of the wave will be

  • 1 ms-1

  • 2 ms-1

  • 1.5 ms-1

  • 1.25 ms-1


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105.

If there were no gravity, which of the following will not be there for a fluid?

  • Viscosity

  • Surface tension

  • Pressure

  • Archimedes' upward thrust


106.

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. If the 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 m/s

  • 5 m/s

  • 0.05 m/s

  • 0.5 m/s


107.

Horizontal tube of non-uniform cross-section has radii of 0.1 m and 0.05 m respectively at M and N. For a streamline flow of liquid, 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


108.

If two soap bubbles of different radii are connected by a tube, then

  • air flows from bigger bubble to the smaller bubble till sizes become equal

  • air flows from bigger bubble to the smaller bubble till sizes are interchanged

  • air flows from smaller bubble to bigger

  • there is no flow of air


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109.

A soap bubble of radius r is blown up to form a bubble of radius 2r under isothermal conditions. If  T  is the surface tension of soap solution, the energy spent in the blowing

  • 3 πTr2

  • 6πTr2

  • 12πTr2

  • 24 πTr2


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110.

A hollow sphere of volume V is floating on water surface with half immersed in it. What should be the minimum volume of water poured inside the sphere so that the sphere now sinks into the water 

  • V2

  • V3

  • V4

  • V


A.

V2

This difference in pressure between the top and the bottom of the object produces an upward force on it. This is called upthrust.

According to Archimedes Principle, the upthrust on an object in a fluid is equal to the weight of the fluid displaced, so the volume of the object multiplied by the density of the fluid.

When a body (sphere) is half immersed, then 

   Upthrust = weight of sphere

       V2 × ρliq × g = v  ×  ρ × g

∴                ρ = ρliq2

When body (sphere) is fully immersed then,

Upthrust = weight of sphere + weight of water pourd in sphere

           V × ρliq × g = V × ρ × g + V' × ρliq × g

               V' = V2


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