I am aware that all the contact forces we experience like tension, friction, normal reaction, et cetera are complex manifestations of the fundamental forces which are gravitational forces, electromagnetic forces, strong and weak nuclear forces.
Suppose now that a body is placed on a stationary table. We say that since it is observed that the body is also at rest in spite of gravitational force acting on it, there must be an equal and opposite force acting on the body to cancel it out and that force is named as the normal reaction.
Normal reaction is said to be fundamentally arising out of electromagnetic interactions between the atoms of surface and body.
I also read that these electromagnetic forces between the surfaces in contact is known as contact force, and there I found that normal reaction is defined as the vertical component of contact force and friction as the horizontal component.
Now, I've a few questions.
Firstly, what makes the normal force, which is just a force due to random interactions of atoms electrically, is equal in magnitude to the gravitational force. I could explain why the normal reaction is opposite in direction, which is the obvious conclusion from how it is defined, but how can all the electric interactions between the atoms be planned so as to result in force equal to the gravitational force. I could not see any connection between the gravitational and electric forces...
The second question that comes to my mind, which is quite silly, but still connected, is that if a very heavy body is kept on a table and the table breaks due to its weight, then is it that the maximum normal force table could exert was lower than the weight of the body and hence it broke.
Another of my question, which I think is wise to put it here as it is all connected, is that, if a body is kept on the floor of a lift and a slight force is acting on the body, such that it is not large enough to move the body(due to friction), and the lift starts accelerating downwards, with the force still acting on body, then normal reaction increases and the contact force remains the same (assumed this, because the surface is the same), then will the friction acting between the body and the floor of lift, will also change.
But, I feel again, that the contact force should also change in this case, but I'm unable to find a reason why it would change. I feel this because it is not possible that one component changes and the resultant does not. I'm not sure of what change in friction would be.
Please help me in all this. You may not answer all of my questions but just give me a direction on how to think on this The reason for these question, I think, is that contact forces and their connection with non contact forces is not discussed very clearly, almost everywhere I've read about it.