Question
Explain why Water with detergent disolved in it should have small angles of contact.
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Answer
Water with detergent dissolved in it has small angles of contact $(\theta).$ This is because for a small $\theta$, there is a fast capillary rise of the detergent in the cloth. The capillary rise of a liquid is directly proportional to the cosine of the angle of contact $(\theta).$ If $(\theta)$ is small, then $\cos\theta$ will be large and the rise of the detergent water in the cloth will be fast.
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