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A glass rod of radius R is dipped into water, which completely wets the glass (contact angle zero). Water rises around the rod. In a gravity-free environment, what is the radius of curvature Rc of the free liquid surface?
- R
- R/2
- 2R
- 4R
Correct answer: R
Solution
When the glass is completely wetted, the contact angle is zero, so the meniscus meets the surface tangentially and forms a hemispherical surface whose radius of curvature equals the radius R of the rod. Hence Rc = R.
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