Formula of weight of surface water

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Homework Help Overview

The discussion revolves around understanding the formula for the weight of water at the surface, specifically expressed as 2(pi)Rσ(cos angle). Participants are exploring the context and implications of this formula in relation to surface tension and capillary action.

Discussion Character

  • Exploratory, Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • Participants are attempting to clarify the derivation of the formula and its components, particularly questioning how the term 2(pi)R is derived and its relevance to the weight of the water column in a capillary tube.

Discussion Status

The discussion is ongoing, with participants seeking additional context and clarification regarding the assumptions involved in the formula. Some have proposed scenarios involving capillary tubes and surface tension, while others are questioning specific aspects of the formula's derivation.

Contextual Notes

There appears to be a lack of complete context regarding the experimental setup or specific conditions under which the formula is applied, as participants are asking for more information to better understand the problem.

goldfish9776
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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

 

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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.
 
haruspex said:
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?
 
goldfish9776 said:
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)?
 

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