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December 3rd, 2017, 07:25 PM   #1
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Hair raising question

Hi All,

I'm studying adhesives and their relevance for removing human hair. My studies have delivered most of the required information, but not all, and I'm hoping that the Forum can help.

It is known that a single human hair requires a Mean Force (N) of 0.65 to remove it.

It is also known that there are roughly two hairs per millimeter of skin.

How do I calculate how much force (N) is required to remove the two hairs per mm? The desired outcome is N/mm.

Last edited by skipjack; December 4th, 2017 at 03:41 PM.
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December 4th, 2017, 01:17 AM   #2
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I assume that is 2 hairs per square mm.
2 hairs will take twice the force, so 1.3N per square mm.
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December 4th, 2017, 08:55 PM   #3
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Quote:
Originally Posted by weirddave View Post
I assume that is 2 hairs per square mm.
2 hairs will take twice the force, so 1.3N per square mm.
Thank you, weirddave! I got hung up thinking that the force was not linear.

Please excuse my ignorance, but let's say that it is not square mm. How does that affect the outcome? For example, say it is 2 hairs per mm of length. In the world of adhesives the unit of measure is N/mm, not N/mm2.
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December 5th, 2017, 12:32 AM   #4
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OK, a bit of reading suggests that it is N/mm per unit width of the adhesive, thus is actually an area. Assuming 2 hairs per mm per unit width of the adhesive, the answer is 1.3N/mm.
Obviously, if you change the width of the adhesive, the calculation has to be adjusted.
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