Calculating the surface tension using the method of Lecomt de Nouy

In summary, the ring has a mass of 4.9 grams and the force applied is 0.089 Newtons. The surface tension is 0.1016 Newtons.
  • #1
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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  • #2
You are given the mass of the ring. Does the force you are given include the weight of the ring?
 
  • #3
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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  • #4
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.
 
  • #5
The weight is ##mg## not ##m##.
 
  • #6
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!
 

FAQ: Calculating the surface tension using the method of Lecomt de Nouy

What is the method of Lecomt de Nouy?

The method of Lecomt de Nouy is a technique used to measure the surface tension of a liquid. It involves measuring the force required to pull a small platinum ring from the surface of the liquid. This force is then used to calculate the surface tension of the liquid.

Why is surface tension important?

Surface tension is an important physical property of liquids that affects many natural phenomena, such as the behavior of droplets, bubbles, and waves. It also plays a crucial role in industrial processes, such as coating and printing, and in biological systems, such as the movement of fluids in plants and animals.

What are the materials needed for the method of Lecomt de Nouy?

The materials needed for this method include a platinum ring, a balance, a micrometer, a thermometer, a stopwatch, and the liquid being tested. It is important to use a platinum ring because it is inert and does not react with the liquid, and the micrometer is used to measure the thickness of the liquid film on the ring.

How accurate is the method of Lecomt de Nouy?

The method of Lecomt de Nouy is considered to be a highly accurate technique for measuring surface tension, with an accuracy of about 0.1 mN/m. However, the accuracy may vary depending on the precision of the equipment used and the skill of the operator.

Can the method of Lecomt de Nouy be used for all types of liquids?

While the method of Lecomt de Nouy can be used for a wide range of liquids, it is not suitable for all types. It works best for low viscosity liquids, such as water and alcohols, and may not be accurate for highly viscous or non-Newtonian liquids. Additionally, the liquid must be free of impurities that could affect the measurement.

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