Mechanical Properties of Fluids

Question

When a sewing needle is gently placed on the surface of water, it floats. Why?

Answer

The water surface below the sewing needle gets slightly depressed when gently placed on the surface of water. The force due to surface tension on depressed curved surface is inclined upwards, whose resultant is vertically upward, which balances the weight of needle. therefore, the needle floats.

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