Friction force calculation of syringe plunger

AI Thread Summary
The discussion focuses on calculating the static friction of a syringe plunger's rubber seal. The user measured the push and pull forces required to move the plunger, with values of 0.625 and 0.677777778, respectively. Initially unsure how to derive the coefficient of friction from these measurements, the user later realized that a free body diagram allowed for the use of the measured forces directly. Another participant questioned the necessity of the coefficient if the friction force was already known. The conversation highlights the importance of understanding friction in mechanical systems.
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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