Hmmm. This isn't going to be an easy answer
because two things can vary a lot:
structure of the bone
2. The direction of the
Bones are made up mostly of protein
and minerals (calcium and others). When we're
born, there's very little mineral. Our bones are
soft, flexible cartilage. These bones don't break
very easily because they bend so well. They don't
allow you to be very strong though, since the
force of your muscles just causes bone bending
instead of moving whatever you're trying to move.
(To see what mineral-free bones are like, put a
wishbone in vinegar for a while.) So to get
strong, we need more rigid bones. The rigidity
also makes bones easier to break. If we use our
muscles, our bones get stronger too. They are
always being broken down and built up a little at
a time. As we get older, we lose bone mass,
particularly if we don't get enough calcium or we
smoke or drink. This makes bones really brittle
because we lack both flexible cartilage and sturdy
bone. Men also have denser bones than women of
the same size.
The direction of the force
makes a difference too. Find a bone picture or
model and look at the long bones of the arms and
legs. Notice that they're not straight? the
bends and shapes make bones better able to take
the stress that they normally are subjected to.
They are often very resistant to force in one
direction, but vulnerable to it in
Want to see how the damage for a
given force varies with the direction? Get small
wooden dowels of the same dimension and subject
them to the same force applied in different ways
(for example, drop the same weight on the end of
one dowel and the middle of another). Use eye
protection and other safety measures.
to see pictures of a fracture, a weird type of
splint, and healing bone? Go to:
http://www.eatonhand.com/IMG/img00019.htm DO NOT
got to this site if you're easily grossed out!
Materials are often characterized by the ultimate
strength which is the stress or pressure required
to cause fracture or breakage.This stress can be
caused by compression, tension, or shear. The
answer for the strength of bone can probably be
found in any
physics textbook (it's a pretty
popular subject). One number I found for tensile
strength is 130 X 10^6 newtons per square meter.
This might be in unfamiliar units though. What is
this value in terms of psi or atmospheres?
That depends on the bone. It is very easy to
fracture a small bone, especially if the pressure
is applied across the weakest point. I'm not sure
exactly how much pressure is needed, but I can
tell you that as little as 25 pounds of pressure
applied to one of your small bones will cause a
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