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Thread: Physics

  1. #1
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    Default Physics

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    Are you sure joints are levers?

    This is what dictionary.com gave me for the definition of a lever:
    Science Dictionary
    lever *(lěv'ər) Pronunciation Key*
    A simple machine consisting of a bar that pivots on a fixed support, or fulcrum , and is used to transmit torque . A force applied by pushing down on one end of the lever results in a force pushing up at the other end. If the fulcrum is not positioned in the middle of the lever, then the force applied to one end will not yield the same force on the other, since the torque must be the same on either side of the fulcrum. Levers, like gears, can thus be used to increase the force available from a mechanical power source. See more at fulcrum, See also mechanical advantage.
    The American Heritage® Science Dictionary
    Copyright © 2002. Published by Houghton Mifflin. All rights reserved.
    Cite This Source

  2. #2
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    Default

    The system of bone/joint/muscle/load is a lever.

  3. #3
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    every muscle is paired with a countering muscle, therefor it's a lever. one pulls and one pushes. extending your elbow is both bicep and tricep, benching/punching is contracting your chest&shoulder and extending your tricep, etc.

  4. #4
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    Here's a site with lots of pictures and explanations of the concept (bones, joints, muscles as levers):

    http://www.sciencelearn.org.nz/Conte...-your-body-use

  5. #5
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    I'd say you might call it a lever **system**. The bone being the lever, the weight being the load, the muscle applying the force, and the lever pivoting on the joint.

    But we know what you mean when you use the term you're using.

  6. #6
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    Default Are you sure?

    What about this?
    "A force applied by pushing down on one end of the lever results in a force pushing up at the other end."
    That definitely does not happen in the system you described.
    Joints and their components seem to be more like pulleys (which someone told me is a type of lever), but I do not think even that label is accurate.

  7. #7
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    Default I'm Pretty Fucking Sure.

    But in case you know differently, why don't you tell us what you think it is.

  8. #8
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    "A force applied by pushing down on one end of the lever results in a force pushing up at the other end."
    So, is everyone here going to ignore that part of the lever definition?

    I went to johnkreg's web site. With their diagrams of levers, the only one which fit the definition of lever was the class 1 lever, but notice that they drew in the effort arm in the example they used; in that example, the effort arm would be the part that goes down, but, like I said, there is no effort arm.

    Can anyone explain why those examples ignore that one of a lever's arms goes up while the other goes down?

  9. #9
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    Really, can we come up with more substantive questions about physics (and this is actually a statics question, but whatever) than semantical arguments about what is and is not a lever? FFS.

  10. #10
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    starting strength coach development program
    The troll-ness is exceedingly thick in here.

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