A clean steel needle can sometimes be placed carefully on the surface of water without sinking even though the density of steel is much greater than the density of water. Which explanation is most appropriate?
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Question

A clean steel needle can sometimes be placed carefully on the surface of water without sinking even though the density of steel is much greater than the density of water. Which explanation is most appropriate?

Options

G1 Physics · Accepted Answer

If the water surface is not broken, the meniscus around the needle becomes curved. Surface tension acts tangentially to the liquid surface along the contact line. The vertical components of these surface-tension forces can provide an upward force that helps support the needle. Ordinary buoyancy may also contribute, but the essential reason a dense needle can remain at the surface is the support supplied by surface tension. Correct option: A.