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Mechanical Properties of Fluids
Question
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Assertion:  A needle placed carefully on the surface of water may float, whereas the ball of the same material will always sink. 

Reason:  The buoyancy of an object depends both on the materials and shape of the object.

  • If both assertion and reason are true and reason is the correct explanation of assertion.

  • If both assertion and reason are true but reason is not the correct explanation of assertion.

  • If assertion is true but reason is false.

  • If both assertion and reason are false.

Answer

C.

If assertion is true but reason is false.

When a needle is placed carefully on the surface of water,  it floats on the surface of water due to the surface tension of water,  which does not allow the needle to sink.

In case of a steel ball, the surface tension of the water is not sufficient to keep it floating, so it sinks down.

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