Sleeping on Nails

How can i explane to a group of 16 year olds how a bed of nails works?
- Sam (age 18)
Physics Org, Duluth

A bed of nails works in terms of the area that the force on the nails is acting over. This has to do with the pressure that each nail is exerting on a body. If there is one nail is on the bed, then all of the force of the body is on the head of the nail. Since this a very small amount of surface area that the force is being applied to, the pressure is very large since P=F/A. This would cause a puncture is most materials, including human skin. If this area is significantly increased by adding a large amount of nails to the bed, then the pressure would be diminished by a large amount. This causes the pressure of each nail to not reach the necessay pressure to break through materials. This would then allow someone to be able to sit on nails and bring wonder to onlookers.

(published on 10/22/2007)