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Newton's theories mainly deal with things in motion. The fact that a person can lie on a bed of nails without being punctured does not follow from any of Newton's laws except to the extent that the force holding the person against the nails is the force of gravity.
The thing that keeps the person from getting holes in the skin is the distribution of forces over very many nails. Think of it this way. Take a single nail and let it rest point down on the skin of your arm. Let's suppose the nail weighs 1/20 of a pound. The weight of that nail will not be sufficient to make a hole in the skin. In fact I could push down on the nail with some force, perhaps up to a whole pound without injury.
Materials:
1. Plywood
2. 2.5 inch nails
3. Hammer
Physics Behind It:
Procedures:
Mark a grid on the plywood with lines 1" apart, parallel to the sides and ends.
Drill a hole at each of the intersections, orthogonal to the board's surface.
Drive a spike through each of the holes.
Sandwich the nail heads between the plywood and the panelling, using the 1" wood screws to secure the panelling to the plywood.
Results:
preassure= force/area
The physics behind the bed of nails is that when you have a lot of nails on the bed, your weight will be distributed between all of the nails that the pressure excerted by each of the nails will not be dangerous because it will not be enough to break the person’s skin. You can even place a second bed on top of you and break a cinderblock on it. The resulting force is distributed over all of the nails, so you shouldn't be injured.
If you step on the point of a nail, your foot exerts a tremendous amount of pressure on the nail's tiny point.
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