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Advantage of doorknobs with long handles

  1. Sep 13, 2007 #1
    Torque question.
    What is the advantage of of doorknobs with long handles instead of standard round ones in terms of decreased force requirements?
     
  2. jcsd
  3. Sep 13, 2007 #2

    learningphysics

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    What is the definition of torque?
     
  4. Sep 13, 2007 #3
    the rotational motion of an object
     
  5. Sep 13, 2007 #4
    True.. more specifically, how is that rotational motion caused?

    What is the equation for torque?
     
  6. Sep 13, 2007 #5

    learningphysics

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    There is a definition of torque that is related to force and the distance from the rotation-axis that the force was applied...
     
  7. Sep 13, 2007 #6
  8. Sep 13, 2007 #7
    the lever arm is the perpendicular distance from the axis of rotation to the line of action of the force
     
  9. Sep 13, 2007 #8
    thats what you talking about right
     
  10. Sep 13, 2007 #9

    learningphysics

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    yes, exactly... so suppose I apply a certain torque with a certain force F1 at a radius r1... but then I double my r from r1 to 2r1... how much force do I need for the same torque as before (keeping the same angle)...
     
  11. Sep 13, 2007 #10

    learningphysics

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    yes exactly.
     
  12. Sep 13, 2007 #11
    twice the force as well
     
  13. Sep 13, 2007 #12
    oops, a smaller force
     
  14. Sep 13, 2007 #13

    learningphysics

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    exactly... only half the force is needed for the same torque...
     
  15. Sep 13, 2007 #14
    Right. Apply this knowledge to your practical usage of doorknobs, the lever one VS. the turning one.
     
  16. Sep 13, 2007 #15
    but i was thinking wasn't the axis of rotation always been considered was at the hinges
     
  17. Sep 13, 2007 #16
    Ok! got it now.
     
  18. Sep 13, 2007 #17

    learningphysics

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    cool.
     
  19. Sep 13, 2007 #18
  20. Sep 13, 2007 #19
    lol.. real time replying is awesome
     
  21. Sep 13, 2007 #20

    learningphysics

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    no prob.
     
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