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My book, in mechanics, claimed that the normal forces were actually a result of electromagnetic force and that the "hand of the strongest weightlifter will crumble under the weight of a feather" if electromagnetic forces did not exist.

I imagine that it was due to some kind of attraction or repulsion between charges in the bodies. But I still cannot understand what exactly the statement tries to say. It also considers friction as a kind of normal reaction, so, I don't understand how the force actually sets up

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The electromagnetic interaction is what stops atoms from being pushed close to each other (up to a point). Electrons are negatively charged so they repel the electrons in other atoms which are also negatively charged. As in this image:

Charge rules

If there was no electromagnetic interaction weightlifters and feathers wouldn't exist in the first place but hypothetically there would be nothing stopping atoms from getting very close to each other.

If you allowed atoms to get close enough to each other you would have to start accounting for the other interactions and who knows what would happen but that is probably outside of the scope of what the question is asking.

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    $\begingroup$ Actually that is not entirely true. How do you explain chemical bonding then? $\endgroup$
    – user256968
    Mar 26, 2020 at 17:06
  • $\begingroup$ Can you highlight exactly what I said that is not true? Chemical bonding relies on the electromagnetic interaction. I wasn't attempting to provide a rigorous explanation of what might happen if the EM interaction vanished, in the context of what is being asked, what I've said is sufficient unless I've missed something completely. $\endgroup$
    – Charlie
    Mar 26, 2020 at 17:11
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    $\begingroup$ Just a doubt. In any case, we are floating above the ground, right? So, how do we manage to push off electrons using our feet (charging by rubbing) without actually colliding with them? Is my line of thought flawed? (Idk much about QM, just a high school student) $\endgroup$
    – Elendil
    Mar 26, 2020 at 17:13
  • $\begingroup$ Hmmm nothing I didn't understand well your answer. $\endgroup$
    – user256968
    Mar 26, 2020 at 17:13
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    $\begingroup$ The push between two electrons isn't much on a human scale, but if you have billions and billions of electrons in atoms that are pushing each other away the force can be enough to hold your entire weight. Asking if we are "floating" above the ground doesn't really make sense since the concept of "touching" loses its meaning at that kind of scale. $\endgroup$
    – Charlie
    Mar 26, 2020 at 17:22

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