Why can a person lay on a bed of nails & not be
injured? What is this scientific theory called? Where can I obtain
information to demonstrate this theory for my science fair? What do I ask
at the library?
This is just a matter of the amount of force per unit area. Certainly if
you were to put all of your weight on just one nail, it would injure you.
If you put all your weight on two nails, each would have to bear just half
the weight. If we increase to two hundred nails, each nail is carrying
just a small fraction of your weight, at which point no serious damage is
done. If you increase the nail density even more, you approach a flat
If you should ever consider using a bed of nails, make sure that you do
this under the supervision of a responsible adult. Check the bed of nails
to make sure that all the nails are at the same height. If one is slightly
taller, it can hurt you. Also, you need to think about how you will get on
and off the bed. As you change your position, you do not want to have all
of your weight on just a few nails. This can happen as you sit up or roll
over the very edge.
---Nathan A. Unterman---
The phenomenon to which you refer has to do with pressure. Pressure is the
weight of an object divided by the total area over which that weight is
distributed. If a person sat down (or laid down) on one nail, hopefully
you realize that it would puncture his skin. This is because the very
small part of the skin that is contacting the nail is not strong enough to
support his entire weight. If his weight is spread out over a sufficient
number of nails, however, each little portion of skin will be supporting a
very small fraction of his weight, and he will suffer no injury.
If you do a web search for "bed of nails," you are likely to find
sufficient reference material for your project.
You take the weight of a person and divide it by the number of nail points
the person is laying on. If the weight per nail point is small enough, the
person doesn't get punctured.
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Update: June 2012