# A Question on surface tension

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1. Nov 17, 2016

### vijayram

1. The problem statement, all variables and given/known data

Water rises in a capillary tube to certain height such that the upward surface due to surface tension is balanced by 7.5 X 10-4N
Force due to weight of the liquid. If the surface tension of water is 6 X 10-2Nm-1,the inner circumference of the capillary must be

2. Relevant equations

pexcess=2T/rcosθ

3. The attempt at a solution

I thought that the force of the excess pressure which causes the movement of liquid must be equal to the weight of the liquid.I know excess pressure is 2T/r (θ=0 for water),but how to find the force of this pressure?Is my approach right?

Can we just like that multiply 2T/r with πr2because it is not plain liquid but a meniscus?

2. Nov 17, 2016

### Staff: Mentor

Yes. The upward force is $(2\pi r) T$. Think of the surface as a membrane with a tensile force per unit length of T.

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