Friction force calculation of syringe plunger

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Discussion Overview

The discussion revolves around calculating the static friction of a rubber seal in a syringe mechanism. Participants explore the relationship between measured forces and the coefficient of friction, focusing on both theoretical and practical aspects of the calculation.

Discussion Character

  • Exploratory, Technical explanation, Conceptual clarification

Main Points Raised

  • Tyler seeks to calculate the coefficient of static friction based on measured push and pull forces for a syringe plunger.
  • One participant suggests that knowing the force applied to press the surfaces together is necessary for calculating the coefficient of friction.
  • Tyler later indicates that he may not need to calculate the coefficient if he can use the measured friction forces directly.
  • Another participant questions the necessity of the coefficient if the friction force is already known.

Areas of Agreement / Disagreement

The discussion shows some uncertainty regarding the necessity of calculating the coefficient of friction, with differing views on whether it is essential given the available data.

Contextual Notes

Participants do not clarify the assumptions regarding the forces applied or the conditions under which the measurements were taken, leaving some aspects unresolved.

ktm_rider
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Hi all,

This is my first post here. I finally decided to sign up after using the site for many years.

I am working on a project involving a syringe mechanism. I am using a stock 6ml syringe. I'm trying to calculate the static friction of the rubber seal.

I have measured both the pull and push forces required to move the plunger, but am blanking on how to actually get the coefficient of friction from those numbers.

The pushing force is:0.625
The pulling force is: 0.677777778

Thank you for all the help!

Tyler
 
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I think you would have to know the force being applied to force the two surfaces together, not sliding back and forth over each other.
 
Hm, okay. Any suggestions on the best way to go about that?

Thank you
 
I think i figured it out.

After drawing out the free body diagram, I can use the actual forces i measured without having to solve for the coefficient of friction.

Thank you for your help Drakkith
 
Why do you need the coefficient if you have the friction force?

(edit: you figured it out while I was posting.)
 

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