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    I was thinking about this today:

    When a force acts on an object, the object exerts on equal and opposite force - Newton's third law. Imagine this situation:

    I am breaking down a wall with a hammer. I begin hitting the wall gently and this wall doesn't break. I then hit harder and the force exerted on the wall increases. As I'm hitting the wall harder, the wall begins to crumble and break.

    What I want to know is:

    - Does the wall have a certain threshold value at which point it cannot exert a force opposite and equal to the force I hit with and begins to crumble? The harder I hit, the more I exceed its threshold value and the more it crumbles and breaks.

    -Why does the wall not fall down completely if I exert a force just above this theorized threshold value? Is it due to friction forces in the planes of atoms? Is it due to the composition of the wall itself? Or is it due to the way atoms are arranged in the wall?
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    (Original post by No!)
    I was thinking about this today:

    When a force acts on an object, the object exerts on equal and opposite force - Newton's third law. Imagine this situation:

    I am breaking down a wall with a hammer. I begin hitting the wall gently and this wall doesn't break. I then hit harder and the force exerted on the wall increases. As I'm hitting the wall harder, the wall begins to crumble and break.

    What I want to know is:

    - Does the wall have a certain threshold value at which point it cannot exert a force opposite and equal to the force I hit with and begins to crumble? The harder I hit, the more I exceed its threshold value and the more it crumbles and breaks.

    -Why does the wall not fall down completely if I exert a force just above this theorized threshold value? Is it due to friction forces in the planes of atoms? Is it due to the composition of the wall itself? Or is it due to the way atoms are arranged in the wall?
    I think this is less to do with the ability for the wall to exert forces, than just simply the bondings of molecules in the wall (be they chemical or otherwise), not being able to withstand the force you applied. Obviously, if you had an infinitely strong wall, you could apply a strong a force to it as you want and it wouldn't break (the unstoppable force and the immovable object). Also, the wall doesn't all fall down, because your force applied isn't exerted on all the wall, just part of it. If you had a hammer the size of the wall and hit it then ,obviously, the whole wall would fall down.

    And just as an extra, F=ma isn't Newton's third law of motion. It's his second.
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    (Original post by dknt)
    I think this is less to do with the ability for the wall to exert forces, than just simply the bondings of molecules in the wall (be they chemical or otherwise), not being able to withstand the force you applied. Obviously, if you had an infinitely strong wall, you could apply a strong a force to it as you want and it wouldn't break (the unstoppable force and the immovable object). Also, the wall doesn't all fall down, because your force applied isn't exerted on all the wall, just part of it. If you had a hammer the size of the wall and hit it then ,obviously, the whole wall would fall down.

    And just as an extra, F=ma isn't Newton's third law of motion. It's his second.
    I suppose the third law could come into the bit where you end up breaking your hammar though =P
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    (Original post by limetang)
    I suppose the third law could come into the bit where you end up breaking your hammar though =P
    Well I would say that Newton's third law applies here more than F=ma
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    The wall has certain bonds in it which require energy to break, not force. As you tap it lightly there is insufficient energy to break any of the bonds so the energy dissipates. When you get over the threshold you rightly identified, there is enough energy to start breaking bonds, it's nothing to do with the force really. The extra force your applying is more a byproduct of giving the hammer extra energy. It also takes a while to fall down because you're only breaking a certain number of bonds with each strike, you're going to need to seperate whole sections of the wall before they start to topple.
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    (Original post by dknt)
    Well I would say that Newton's third law applies here more than F=ma
    True, although in this situation I'd say that all three laws of motion and his law of gravitation all come into play.
 
 
 
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