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Energy Triangle

  1. May 13, 2010 #1


    gPE to KE - Water in waterfall
    KE to gPE - Climbing mountain
    Strain to KE - Firing an arrow
    KE to Strain - Trebuchet being wound back
    Strain to gPE - ????
    gPE to Strain - ?????

    It is the last 2 for which I really cannot think of instances in life - PLEASE help me out!
  2. jcsd
  3. May 14, 2010 #2


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    hi yeah:)! :smile:
    I don't really like these answers …

    when you climb a mountain (or a ladder), the force from your muscles is immediately converted to gPE … saying that it temporarily becomes KE is missing the point.

    Same thing for the trebuchet … your muscles immediately increase the strain in the trebuchet.
    erm … that's cheating! :redface:

    it's the same as pulling a bow, which the question has ruled out (the arrow itself has no strain, does it? so the strain is in the bow :wink:)

    Try to think of an example where horizontal motion of one thing is converted into strain of another thing (or vice versa). :smile:
    Try the others again first. :smile:
  4. May 19, 2010 #3


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    Hi Yeah:)! :smile:
    What's kinetic about that? If a cat jumping comes from strain (your last example), doesn't all muscular activity?
    Yes. :smile:
    yes, but why a paper airplane … it's almost the only thing that wouldn't necessarily lose height to start with! :wink:
    Why not just throw it up!? :wink:
    You're not a grasshopper or a frog … I know the brain etc can put human muscles into strain, but I don't think external forces can.

    Why not just step onto scales?
    I suppose so. :smile:
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