Calculate Surface Tension of Blood Plasma: Help Needed

Click For Summary

Discussion Overview

The discussion revolves around calculating the surface tension of blood plasma using a specific experimental setup involving a wire ring. Participants explore the relationship between force, radius, and surface tension, addressing a homework problem related to this topic.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Technical explanation

Main Points Raised

  • One participant presents a problem involving lifting a wire ring from blood plasma and seeks help with the calculation of surface tension.
  • Another participant emphasizes the forum's policy requiring the poster to show their work or clarify discrepancies in their answers.
  • A participant suggests that surface tension can be calculated as force divided by length, proposing that the length should be twice the radius of the ring.
  • Further clarification is provided regarding the need to consider the circumference of the circle when calculating the effective length for surface tension.
  • One participant calculates surface tension and discusses the importance of accounting for the surface tension acting on both sides of the wire loop.
  • A later reply provides a numerical estimate for the expected surface tension, suggesting that the initial answer was significantly different from what was anticipated.
  • Ultimately, a participant confirms that they arrived at the correct answer after considering the advice given in the discussion.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the initial calculation method, but there is a collaborative effort to refine the approach to arrive at a correct answer. Discrepancies in expected results are acknowledged, and participants work through the problem together.

Contextual Notes

Participants express uncertainty regarding the correct application of formulas and the interpretation of the problem, particularly in relation to the effective length used in the surface tension calculation.

lovelylm1980
Messages
18
Reaction score
0
can anyone help me out with this question:In order to lift a wire ring of radius 2.07 cm from the surface of a container of blood plasma, a vertical force of 1.90×10-2 N greater than the weight of the ring is required. Calculate the surface tension of blood plasma from this information.
I can't figure it out it seemed so easy at first but then i got the wrong answer.
 
Physics news on Phys.org
Details? This looks like homework --- forum policy is that you show us your work, or state the difference between your answer and what is expected.
 
surface tension is equal to force over length so what i though is that since the force and radiua are given that length L would be the radius times two and to get surface tension the force that is given would be divided by this number, but that's not right because it was the wrong answer.
 
You got half the number expected?

Too late at night, I meant you got a surface tension "twice" what was expected.
 
Last edited:
do you mean that i should take my answer and divide by two or multiply by two?
 
Post your answer --- we'll go from there.
 
surface tension= F/L
2.07 cm= .0207m
L= .0207m x 2= .0414m

1.90×10-2 N/ .0414m= .458 N/m
where do I go from here?
 
Got bumped off for a minute --- Okay, now we get somewhere:
1) remember the formula for circumference of a circle? 2πr

2) when you're pulling the loop from the surface of the liquid, you noticed that the surface "draped" BOTH directions from the wire? Does it make sense to you that you're actually pulling against surface tension exerted against twice the circumference of the wire loop? Once around for the outside of the loop, and once more for the inside?

3) What I come up with on the back of the envelope, and I'm truncating --- you'll have to take it beyond the single significant digit, is 0.07 N/m.

I thought at first that you were hung up on just the trick of doubling the circumference of the loop for this type of measurement --- that's why I said "half" mistakenly, and corrected things to guess that you were getting "twice" the value you were expecting, but it's more like 6 times larger than what your answer key is looking for.

This work for you?
 
Thanks a lot! You really helped me Igot the answer of 0.0731 N/m, and it was right thanks again.
 

Similar threads

Undergrad Du Nouy Method for Measurement of Surface Tension
  • · Replies 23 ·
Replies
23
Views
3K
Tension in a deformed cylindrical bag on a surface
  • · Replies 18 ·
Replies
18
Views
2K
Undergrad What Are Simple Methods to Measure Surface Tension at Home?
  • · Replies 1 ·
Replies
1
Views
4K
High School Calculate Tension of Two Wires: Physics/Precalc
  • · Replies 3 ·
Replies
3
Views
2K
Calculation of the weight of an insect floating by surface tension
  • · Replies 1 ·
Replies
1
Views
3K
Undergrad Help Calculating Pressure of Seawater against a flat surface
  • · Replies 9 ·
Replies
9
Views
3K
High School Non-physicist needs your help torquing a nut!
  • · Replies 9 ·
Replies
9
Views
2K
Shape of a bubble inside a rotating container
  • · Replies 5 ·
Replies
5
Views
2K
Centripetal acceleration blood plasma problem
  • · Replies 6 ·
Replies
6
Views
10K
Calculating Centrifugation Distance and Acceleration for Blood Plasma Separation
  • · Replies 1 ·
Replies
1
Views
10K