Cranking the quantities offers me 1,394 nails—which is in fact not that a lot of. A 40-by-40 sq. grid is 1,600 nails, and which is far more than you need to avert a pores and skin puncture.
So, what if you change the nails with a bunch of damaged glass? It’s really the exact same factor. Confident, glass might be sharper than nails, but it also has some flat areas. As very long as the get in touch with location is large enough, the glass won’t damage anybody.
So that’s the top secret: It won’t take hard skin, just some physics.
Smashing Rocks, Mass, and Acceleration
Now, let us go on to the element of the demonstration when a soldier smashes a rock on leading of the dude’s chest as he lies on the bed of nails. The important physics lesson listed here involves Newton’s second regulation. This is a connection involving the net force on an object (Fnet), the mass of the item (m), and the object’s acceleration (a). If the item is constrained to only transfer in one dimension (to make items easier), then we can symbolize this as the pursuing equation:
The acceleration of an item tells you how that object’s velocity variations. So, if the matter is just being nonetheless, then the velocity will continually be zero, which would be a zero acceleration. Even so, even if the item is going, it can have a zero acceleration as extended as its velocity would not alter. If the item is raising in pace, then it would have a optimistic benefit for the acceleration. That indicates that when an object slows down, it has a destructive acceleration. (Observe: This assumes motion in a single dimension.)
Here’s an case in point: Suppose two folks are every single standing on a skateboard. (These are zero-friction skateboards—you can discover them at the physics retail outlet.) On 1 board is an grownup with a mass of 80 kilograms, and on the other is a child with a mass of 40 kilograms. If I drive on the adult with a power of 80 newtons, it will present an acceleration of 1 meter for every 2nd per second (1 m/s2). If I force with this very same pressure on the baby, the acceleration will be twice as substantially (2 m/s2), because the kid’s mass is half that of the grownup.