MadSci Network: Medicine
Query:

Re: How is it possible to walk on broken glass?

Date: Thu Nov 11 17:34:11 2004
Posted By: Erik von Stedingk, Biotech Sales Manager
Area of science: Medicine
ID: 1097623608.Me
Message:

Hi Steven,

Although your question is far away from my area of knowledge 
(biochemistry), I think I can answer your question. It’s more about 
physics really.

If you make a mat of thousands of nails, pointed side up, with about half 
a centimeter between each nail, I would have no problem to sit down on 
it. This is because each nail takes only a small portion of my weight, 
probably not even enough to prick the tiniest hole in my trousers. If you 
would space the nails five centimeters apart, I would still sit on your 
mat, but I would be more careful with my movements. I might also get a 
few holes in my trousers. Here each point takes a larger part of my 
weight but, my skin being elastic as opposed to the tissue in my jeans, I 
will only suffer from an array of red sore dots on my buttocks. Now, if 
you would ask me to sit on one (1) seven-inch nail stomped through a 
plank, I would certainly protest wildly! Excuse the pun, but do you get 
my point? ;-)

If you spread loads of small pieces of broken glass on the floor and then 
walk over them putting down your feet very levelly (no heels first, and 
not tip-toeing) chances are that the force on your soles will not be 
enough to cut your skin.

Another important factor is that the feet should be dry: wet skin tears 
more easily. I don’t know if you’ve seen a trick sometimes performed my 
magicians and fakirs: walking up a ladder built of sharp swords. Here 
they usually treat their soles beforehand to make them dry but still 
elastic.

I hope this answers your question!
Kind regards,

Erik



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