While reading about the normal reaction for different scenarios, I faced minor confusion regarding their origin.
Suppose a mass is kept on a surface. The mass exerts a downward force indirectly due to its weight, and the surface would exert a force back on the mass. I wonder where this force is coming from.
One explanation claims that this force comes from the electrostatic repulsion between the two masses and the exclusion principle, which sounds right, obviously.
Another explanation uses the fact that the mass compresses the surface a bit, which tries to restore itself by pushing the mass upwards i.e. against the compression. This is the source of the normal reaction force.
My doubt is, isn't it a bit of both of the above effects? I've seen all sources use one of the two explanations above, but never both of them together. Shouldn't both of these be responsible for the normal force ?
Imagine the surface is perfectly rigid, there is no compression. It would still exert a normal force on the mass. But this force would be purely electrostatic, as there is no compression on restoring force involved.
In the general case however, the mass applies a force on the surface, greater than the normal force due to pure electrostatic repulsion. Hence the surface gets compressed, and the restoring force steps in the balance the forces to bring both of the bodies to rest.
So, am I correct in claiming the following :
$N_{net} = N_{electrostatic} \space+\space N_{restoring}$
In case of a perfectly rigid floor, only the first one works. For a general floor, the first one is not strong enough to resist compression, so the second restoring force walks in to balance the system. If both the forces are not enough, the surface breaks or gets punctured or something.
But is it correct to stay, that there are these two distinct effects that give rise to the net normal force. That the force is a result of electrostatic repulsion and the restoring force due to compression ?
Or are both of these effects the same thing, which doesn't seem to make sense intuitively, as they have different origins, but contribute to the net normal force. Using only one of the explanations above is incomplete. For example, using the restoring force explanation, fails to mention, why a perfectly rigid body would exert a normal force. On the other hand, using the purely electrostatic expression fails to mention, why a heavy object would bend a surface. We clearly need both of them.