Physics Question?

Question

How is surface tension illustrated by water on a coin?

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Answer 1

The angle the water drop makes with the coin indicates its surface tension. A water drop on a coin makes an acute angle where it's in contact with the coin. This shows its surface tension is quite low. Water containing detergent or soap makes an even smaller angle, showing its surface tension is smaller still. A drop of mercury on the coin makes an obtuse angle where it's in contact with the coin, showing it has a high surface tension.