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Pulley - Bar & Weight Question

  1. May 5, 2009 #1
    1. The problem statement, all variables and given/known data
    The bar is maintained horizontal & in equilibrium by an angled string which passes over a pulley and which carries a mass of 2kg at it's free end.

    1) Calculate the Tension T in the String

    2) Show that the mass of the bar is approximately 3.5kg

    2. Relevant equations

    -

    3. The attempt at a solution

    Included the picture there, it's a really easy question I guess but i think i'm missing something :confused:, or not understanding something very well...

    for 1) I presume it's simply 19.6 N , the weight of the mass.

    2) I'm a bit stuck here, what does it want you to use? If 19.6 in the tension in the string and you resolve it vertically I get 19.6cos 30 = 16.97 N which obviously doesn't work out to be 3.5kg, I think i'm missing something regarding the pivot, or maybe it's related to work done...

    Any help would be great, it's just a stupid problem! :P

    Edit: Using that work done thing - I got

    (0.8 * 3.5) / cos (30) = 3.23 but still that's far off, so i don't think it can be that
     

    Attached Files:

    Last edited: May 5, 2009
  2. jcsd
  3. May 5, 2009 #2
    Moments:wink:
     
  4. May 5, 2009 #3
    =P thanks
     
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