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Homework Help: Quick Statics Question

  1. Oct 2, 2011 #1
    Here is my question:
    On this figure, there is a 50 N force on the bigger pulley. When summing up the moments about the x-axis, why isn't -50(0.15) [circled on figure] the same as (-50cos45)(0.15) + (-50sin45)(0.15), which is the sum of the moments of its components?
  2. jcsd
  3. Oct 2, 2011 #2


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    I have a 22" monitor, but that image is still too small to read anything???
  4. Oct 2, 2011 #3


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    I was able to see the image. The 50 N force is applied to the pulley tangent to its circumference at a point 45 degrees counterclockwise from its vertical z axis. It is not applied at the top of the pulley. When you break it into its components, the perpendicular distance is not 0.15 m. Either calculate the perpendicular distance, or use the cross product rule, when calculating the sum of moments this way, and you get the same result.
  5. Oct 2, 2011 #4
    This helped me. Thanks.
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