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Normal Forces

  1. Nov 29, 2009 #1

    I am wondering why normal forces 'are'?

    I mean, I know what they 'do', but why does a surface create a force when a force is put against it? Obviously, it follows Newton's law of equal and opposite reactions, but can anyone explain what happens, if even on an atomic level, to create said force? What's going on under the hood?

    Is this part of a more specific area of physics?

  2. jcsd
  3. Nov 29, 2009 #2


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    What I can tell you is that contact forces like friction, normal force, etc are fundamentally electromagnetic in nature. Atoms can't occupy the same space because they consist of charged particles that interact when they get close to each other. The concept of "touching" becomes meaningless on these scales. I'm sure others can provide further details.

    EDIT: The answer to your question of whether another area of physics becomes relevant when describing things on these scales is, "yes."
    Last edited: Nov 29, 2009
  4. Nov 29, 2009 #3
    My teahcer explained it kind of-probably-very unscientifically, but it seemed to help the class:
    He started with his water bottle. What he said was that the millions of billions of trillions of atoms in the bottle are always pushing against each other in the molecules which always push each other. That's why the bottle doesn't move and fall apart. It's solid, and it stays how it is because all the atoms and molecules are equal and they push with the same force.
    Now, if you put the bottle on a table, the bottle's atoms and molecules are not only pushing against themselves, but also against what surface area they come in contact with: the table. And while the bottle's force is pushing on the table, the table's force has to push back the same amount to keep it from moving. That's the basic principal of normal force.

    Sorry if that didn't help; it's much easier to explain it in person. -crissa
  5. Nov 29, 2009 #4


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    Simple answer: atoms all have an electron cloud. Electron clouds repel each other.
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