A Question on surface tension

  • #1
26
1

Homework Statement


[/B]
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

Homework Equations



pexcess=2T/rcosθ


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?
 

Answers and Replies

  • #2
21,153
4,671
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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