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Homework Help: Very very noob calculation verification [BEDMAS]

  1. Aug 9, 2010 #1
    1. The problem statement, all variables and given/known data


    3. The attempt at a solution
    i calculated and got like

    x'=3.291*104 ---->this does not match with answer key, but im sure its correct.
    could some one verify this pls

    t'=-4.618*10-5---. this makes sense
  2. jcsd
  3. Aug 9, 2010 #2


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    It can't be correct, it doesn't have the right units.

    What calculation did you do? Show your work...
  4. Aug 9, 2010 #3
    i did the exact thing as the solution, i think they converted the x'=32917.5m to x'=32.9km and did not indicate it...
  5. Aug 9, 2010 #4
    x' should be less than x. t' should be greater than t. Also a negative time interval doesn't make sense.
    Last edited: Aug 9, 2010
  6. Aug 9, 2010 #5
    -ve means it happend before no?
  7. Aug 9, 2010 #6


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    They're the same thing (except for rounding), it's not necessary to indicate anything for that conversion.

    And a negative time interval could make sense, if it's the time difference from A to B and B happened before A.

    Anyway, I still don't see your work. Unless the image you show is actually the work you did? I thought it was the given solution.
  8. Aug 9, 2010 #7


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    Aha: I just checked the calculations in the image you showed. I can't say whether the calculation is set up correctly, but there is definitely an error. When I plug
    [tex](1.155)\bigl[3.0\times 10^4\,\mathrm{m} - (0.5)(3.0\times 10^8\tfrac{\mathrm{m}}{\mathrm{s}})(1.0\times 10^{-5}\,\mathrm{s})\bigr][/tex]
    into my calculator, I get [itex]32.9\,\mathrm{km}[/itex]. So the result shown in the image is off by a factor of 1000 - probably whoever did that calculation wrote the wrong units on the result.
  9. Aug 10, 2010 #8
    its from a solution Manuel. im 100% sure its wrong off by a factor of 1000
  10. Aug 10, 2010 #9
    as i think is said it the solution give nis the same as my work that how i did it then when i looked at solution it was the same but off by 1 factor of 1000..so i was confused so i asked thanks for the help
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