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Does a lever/fulcrum reaction demonstrate Newton 3rd Law?

  1. Jan 21, 2016 #1
    Say a lever is tilted on a fulcrum with an object on the side in contact with the floor, a mass falls onto the other side, causing the object to go flying. Does this demonstrate Action-reaction ? (action on the lever to action on the object)
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  3. Jan 21, 2016 #2


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    No. At least not in the way you seem to imply. There are seversl force pairs involved here.
  4. Jan 21, 2016 #3


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    I agree. N3 refers to conservation of momentum. Third law pairs are present in more than one instance here - but, of course, they are to be found everywhere in mechanics.
    I already commented in a recent thread on the same topic that N3 is not the only law that needs to be applied in solving Mechanics problems. Newton stated three laws and he would only have produced one if three were not needed.
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