Calculating the surface tension using the method of Lecomt de Nouy

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Homework Help Overview

The discussion revolves around calculating surface tension using the Lecomte de Nouy ring method. Participants are addressing discrepancies in calculated values and the interpretation of the relevant formula.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • The original poster attempts to apply the formula for surface tension but questions the accuracy of their result compared to provided solutions. Other participants inquire about the inclusion of the ring's weight in the force calculation and suggest clarifications regarding the formula's terms.

Discussion Status

The discussion is active, with participants exploring different interpretations of the formula and its components. Some guidance has been offered regarding the correct interpretation of mass versus weight, which has led to a realization by the original poster about their earlier misunderstanding.

Contextual Notes

There is a mention of specific values for the mass of the ring and the force just before tearing, as well as the temperature of the water, which may influence the calculations. Participants are also reflecting on the implications of these values in the context of the formula used.

arhzz
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Homework Statement
The surface tension can be determined using the Lecomte De Noüy ring method. The mass of the ring is m = 4.9 g and the diameter d = 64.1 mm. The tensile force just before tearing is in water at 25 ° C is F = 0,089 N. Calculate the surface tention
Relevant Equations
y = F/4*pi*r
Hello! I am having unexpected difficulties with this problem.A friend showed me an article regarding the Lecomde ring method,and at the bottom was this little problem that to solve.I've done it like this.

$$ y = \frac{F}{4\pi r} $$ where F is the given force and r is = 0,0325 in meters. The value I get is y = 0,22 N/m. But according to the solutions this is wrong,the right solution should be y = 0,1016 N/m.I highly doubt they are wrong,which means I made a mistake somewhere but I don't see where.The only formula that appered in the article was this and the usual surface tension.What am I i missing here.Thank you!
 
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You are given the mass of the ring. Does the force you are given include the weight of the ring?
 
arhzz said:
Homework Statement:: The surface tension can be determined using the Lecomte De Noüy ring method. The mass of the ring is m = 4.9 g and the diameter d = 64.1 mm. The tensile force just before tearing is in water at 25 ° C is F = 0,089 N. Calculate the surface tention
Relevant Equations:: y = F/4*pi*r

What am I i missing here.
You are misinterpreting the formula. The one here gives the expected answer and explains how the terms are put together.
 
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Okay so I've tried using the formula where the mass of the ring is take into account.

$$ F = m + 4
\pi * r * y $$

If I try to get y out of this it should look like this; $$ y =
\frac{F-m}{4
\pi r} $$

But I still do not get the wanted result.
 
The weight is ##mg## not ##m##.
 
kuruman said:
The weight is ##mg## not ##m##.
Ohh,it said wait not mass,my bad I didnt read carefully.Now I get the right result,sorry for the silly mistake and thank you for your help!
 

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