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Mechanical Properties Of Fluids

Question
CBSEENPH11026280

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

Solution

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