Physics Help Forum How To Measure The Mass And Balance Point Of A Human Limb?

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 Jun 13th 2018, 02:07 PM #1 Junior Member   Join Date: Jun 2018 Posts: 1 How To Measure The Mass And Balance Point Of A Human Limb? Preferably the forearm. I can't spend big money on x-rays, nor can I chop my arm off. I've asked this elsewhere - LINK I know the volume of my forearm, using the Archimedes method, for 10 equal segments of my forearm. I've also looked at x-rays to work out roughly tissue distribution. Only issue, in terms of precision, is there is quite a big difference in density between bone, fat and muscle. On average, bone is 1.7500 g/cm and muscle is 1.0599 g/cm3.
 Jun 14th 2018, 02:40 AM #2 Senior Member     Join Date: Jun 2016 Location: England Posts: 707 I think your idea of defining several segments of the arm is definitely the way to go. For each segment make an estimate of bone and muscle mass and distribution and thus estimate the mass and balance point of each segment. You can then combine the (estimated) mass and balance point of each segment to obtain an estimate for the entire arm. __________________ ~\o/~
Jun 14th 2018, 07:25 AM   #3
Senior Member

Join Date: Apr 2017
Posts: 434
 Originally Posted by kief90 . On average, bone is 1.7500 g/cm and muscle is 1.0599 g/cm3.
Interesting figures ... a search shows human fat is 0.918 ....

Of course the body as a whole is almost exactly 1 , with no air in the lungs, so there must be air space in the intestines and colon etc to make us float.

A search reveals that Archimedes method is a geometric analysis for determining area and volume ...

Archimedes principle involves displacement of water , and this is the rout I would go ...

fill a large container to the brim with water , slowly immerse your fingers , catch and measure the water that overflows , then immerse the whole hand catch and measure the water ... in this way you can get an accurate measure of the volume profile of your arm ....

to get the mass you have to take a guess at the density , perhaps 1.2 ?...

or buy a leg of lamb from the butchers and find the density of that , it's probably quite similar.

Here's someone floating in the dead sea density , 1.24 . I get the impression the arms are floating...

 Tags balance, human, limb, mass, measure, point

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