I know this question may seem obscure, but I'm trying to get a deeper meaning to what allows us to "push" things at a macroscopic level. And since all forces can be broken down or derived from the 4 fundamental forces (as I have read), I'm assuming its the EM force, (repulsion of electrons in atoms?). Please correct me if I am wrong! Cheers!

  • $\begingroup$ I don't know much of higher physics , but unless I'm mistaken most contact forces are manifestations of the electrostatic force $\endgroup$ Oct 9, 2022 at 16:01
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    $\begingroup$ The "four fundamental forces" concept is the product of mathematical abstraction. "Pauli force", a major component of the contact force between solid objects, isn't one of the four. But it's very real, and very fundamental. $\endgroup$
    – John Doty
    Oct 9, 2022 at 23:10
  • $\begingroup$ You're correctly assuming it's EM force, "van der Waals force" specifically. $\endgroup$ Oct 10, 2022 at 2:25

3 Answers 3


The electromagnetic force due to interactions among the molecules or atoms of the objects allows objects to be pushed (compression) or pulled (tension). The microscopic details can be complex.


Rather than "applied force," the correct term is "normal force." "Applied" is not a type of force in a classification scheme.

The normal force requires both electromagnetic interactions and the Pauli exclusion principle. The question of how normal forces arise microscopically is essentially the same as the question of why bulk matter is stable. The definitive paper on this is Lieb, Rev Mod Phys 48 (1976) 553.

  • $\begingroup$ Thank you for taking the time to answer my question! As I understand it applied forces are the forces as a result of two objects coming into contact with each-other, no? $\endgroup$
    – Jake
    Oct 9, 2022 at 16:34
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    $\begingroup$ @Jake - Each atom has negatively charged electrons orbiting it. As two objects approach eachother, the repuslive force between the electrons of each grows exponentially. Nothing ever truly touches. $\endgroup$ Oct 10, 2022 at 8:55
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    $\begingroup$ I don't see how 'applied force' is wrong in this context. A force that is applied to an object is an applied force. The fact that Jake happened to name examples of the normal force is not necessarily relevant because you can also push an object using friction: put a box in front of you, use both hands to push against the sides of the box and then make it move forward (although you could also call this dragging). $\endgroup$ Oct 10, 2022 at 13:51

It depends on the level of detail you are looking for. In Newtonian mechanics they just touch. In classical mechanics and early quantum mechanics, the electrons repel each other. in quantum electrodynamics photons carry the forces between the electrons.


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