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Confirmation or correction required for this problem since the solution has a mistake

  1. May 18, 2012 #1

    s3a

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    1. The problem statement, all variables and given/known data
    The problem along with its solution is attached as Problem 1-5.jpg.

    2. Relevant equations
    Trigonometry.

    3. The attempt at a solution
    Should the 60° angle in Fig. 3 be 30°? Is Fig. 3 supposed to be the exact same thing as Fig. 2 except that the force is moved to be entirely horizontal? I'm just trying to make sure that I'm visualizing things properly so sorry for the probably trivial question. I was confused by the 60° angle and then I noticed that d = 30sin(60°) ≠ 15 inches and that if I assumed that Fig. 3 was the exact same thing as Fig. 2 with the force relocated then d = 30sin(30°) = 15 inch which makes sense to me. I'm just looking for a confirmation unless I am wrong, then I am looking for a correction.

    Any input would be highly appreciated!
    Thanks in advance!
     

    Attached Files:

  2. jcsd
  3. May 18, 2012 #2

    gneill

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    Staff: Mentor

    Re: Confirmation or correction required for this problem since the solution has a mis

    Yes, it looks as though they've used the wrong figure; the angle should be 30° to match the rest of the example. Interestingly, they've patched in the correct result even though the calculations are incorrect. Note, for example, that they arrive at length d = 15 inches using d = 30 sin(60). Well sin(60) is not 1/2; sin(30) is.
     
  4. May 23, 2012 #3

    s3a

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    Re: Confirmation or correction required for this problem since the solution has a mis

    Thank you.
     
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