I just learnt that friction is the electromagnetic force.

How does the electromagnetic force work during sex? The electrons on my knob repel the electrons of her vagina and that makes us cum? How does pressure play into this? It's nicer for both of us when she puts her legs together for example.

How does the nervous system play into this too? When friction is occurring, how does the brain realise this and what forces are at play? To put it more bluntly and in a stupid way, my cock rubs against my underwear all the time but I don't spontaneously orgasm every couple of minutes.

Does sex only concern the electromagnetic force or are there other forces included? Gravitational force is relevant for certain positions I suppose.

Where can I learn more about the physics of the human anatomy beyond biomechanics?