Cranking the number gives me 1,394 nails – which isn’t actually that much. A 40-by-40 square grid is 1,600 nails, and that’s more than you need to prevent skin stinging.
So, what if you replace nails with a bunch of broken glass? It’s really the same thing. Of course, glass can be sharper than nails, but it also has some flat parts. As long as the contact area is large enough, the glass will not hurt anyone.
So it’s a secret: it doesn’t take tough skin, just some physics.
Smashing rocks, mass and acceleration
Now, let’s go to the demonstration part when a soldier breaks a stone on the boy’s chest while he is lying on a bed of nails. The main text of physics here deals with Newton’s second law. It is a relationship between the net energy on an object (F)Net), Mass of the object (m), and acceleration of the object (a). If the object is limited to moving only one dimension (to make things easier), we can represent it as the following equation:
The acceleration of an object tells you how the velocity of the object changes. So, if the thing is just stationary, the velocity will be constantly zero, which will be a zero acceleration. However, even if the object is moving, its acceleration can be zero until its velocity changes. If the object increases in speed, it will have a positive value for acceleration. This means that when an object slows down, it has a negative acceleration. (Note: This assumes a level of speed.)
Here is an example: Suppose two people are standing on a skateboard. (These are zero-friction skateboards — you can find them in physics stores.) One board has an adult weighing 80 kilograms, and the other a child weighing 40 kilograms. If I push on an adult with 80 Newton force, it will give a speed of 1 meter per second (1 m / s)2) If I apply pressure on the baby with this same force, the acceleration will be doubled (2 m / s)2), Since the mass of the child is half that of the adult.