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I know that this is a total novice question. When I push a book from point A to point B, a force is applied by me. The book has mass and some acceleration was also achieved in this example. I recently read about the fundamental forces of nature. They included Gravitation, Electromagnetism, Strong interaction, and weak interaction. I have no deep knowledge regarding any of the 4 forces. A simple explanation would be appreciated. My question is :

In the act of pushing a book, which of the 4 fundamental forces of nature come in the picture? Which one force could I relate to this event?

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    $\begingroup$ The electromagnetic one. The atoms of your finger come close to the atoms of the book. Those atoms eventually repel each other, and that electromagnetic repulsion force is what pushes the book forward. $\endgroup$
    – Steeven
    Commented Feb 26, 2019 at 5:41
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    $\begingroup$ Also How can I stand on the ground? EM or/and Pauli? $\endgroup$ Commented Feb 26, 2019 at 5:53
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    $\begingroup$ And Is the electromagnetic force responsible for contact forces? $\endgroup$ Commented Feb 26, 2019 at 5:54
  • $\begingroup$ Thanks for the above references. They were of great use but quite difficult for novice like me! $\endgroup$
    – user223877
    Commented Feb 26, 2019 at 6:07

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It's certainly not gravity (your mass is too low), and the strong + weak interactions have very short range. So by elimination, it's the electromagnetic force. This is the same force that governs interactions between atoms.

With the exception of gravity, every force you can see in ordinary life - e.g. the force that holds your body in one piece, the force that prevents the book from falling through the table - is due to the electromagnetic force.

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  • $\begingroup$ @ Allure thanks for the short and sweet explanation. $\endgroup$
    – user223877
    Commented Feb 26, 2019 at 6:04
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The electromagnetic interaction is the main interaction in pushing the book , as all matter is composed of atoms and molecules whose interaction to other atoms and molecules in bulk matter ( your hand on the book) goes via the electromagnetic interaction.

It is the electromagnetic repulsion ( plus Pauli exclusion principle but it is another story) that keeps the book on the table. The electromagnetic interaction leads the biochemistry and transfers energy to your muscles to be able to transfer energy to the book.

At the classical observable level it is gravity, and electromagnetic interactions. The strong and the weak are effective at small distances where a quantum mechanical framework describes all four interactions ( almost, as gravity is not yet definitively quantized)

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  • $\begingroup$ Thanks for the explanation @anna v! A question for you. Can you give a gist of what Pauli principle is? Only just the basic idea or definition. $\endgroup$
    – user223877
    Commented Feb 26, 2019 at 6:03
  • $\begingroup$ It has to do with the mathematics of quantum mechanics, where particles are identified with an intrinsic angular momentum called spin. If a particle has spin 1 it can occupy the same energy state as other particles of spin 1,. If it has spin 1/2 it cannot occupy the same level with anothe spin 1/2. Electrons which are the outer surface of atoms have spin 1/2 . $\endgroup$
    – anna v
    Commented Feb 26, 2019 at 7:00
  • $\begingroup$ When an electron is pushed it cannot move to a state where another electron is, so there is an effective resistance to applied forces, which together with the electron electron electromagnetic repulsion keeps solid matter solid. In cosmological situation, neutron stars for example, the large gravitational forces destroyed the atoms and nuclei overcoming the Pauli exclusion by destroying the energy levels. $\endgroup$
    – anna v
    Commented Feb 26, 2019 at 7:00
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When you push a book across a table you will feel that there is friction resisting your push. Friction is what happens when microscopic bumps on the book and table collide. These collisions are ultimately electromagnetic.

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