Formula of weight of surface water

[goldfish9776]

Homework Statement

Why the weight of water at water surface is given by formula 2(pi)Rσ(cos angle) ?

Homework Equations

The Attempt at a Solution

 

[haruspex]

Is there more context to this?
My guess is that a capillary tube has been inserted into water reservoir, resulting in a column of water rising height h (compared with the water remaining in the reservoir). The weight of this column is held up by surface tension in the meniscus. Phi will be the angle of contact of the meniscus.

 

[goldfish9776]

Is there more context to this?
My guess is that a capillary tube has been inserted into water reservoir, resulting in a column of water rising height h (compared with the water remaining in the reservoir). The weight of this column is held up by surface tension in the meniscus. Phi will be the angle of contact of the meniscus.

how about 2(pi)R ? how it comes?

 

[haruspex]

how about 2(pi)R ? how it comes?

Surface tension is a force per unit length. What is the length of contact between the water surface and the capillary (radius R)?