Physics Help!

Discussion in 'Everything Else' started by arthurracoon, Sep 11, 2006.

  1. arthurracoon

    arthurracoon The Cardinal Smiles

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    I have a hw due today at 1pm

    this is the last problem on the assignment...some help?

    City A lies directly west of city B. When there is no wind, an airliner makes the round trip flight of distance s between them in a flight time of t1 while traveling at the same speed in both directions. When a strong, steady wind is blowing from west to east and the airliner has the same air speed as before, the round trip takes a flight time of t2.

    How fast is the wind?
     
  2. arthurracoon

    arthurracoon The Cardinal Smiles

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    I have the velocity when theres no wind: v = 2s/t1
    i think i also have the avg velocity when there is wind: Vavg = s/t2
     
  3. PortlandCardFan

    PortlandCardFan Registered User

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    42...













    IHNFC (there is a reason I was a jarhead!!)
     
  4. CaptTurbo

    CaptTurbo Registered

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    Is this an African or European flight?
     
  5. Divide Et Impera

    Divide Et Impera Registered User

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    I just forwarded this thread to your instructor for cheating....
     
  6. Divide Et Impera

    Divide Et Impera Registered User

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    :)
     
  7. nathan

    nathan Moderator Contributor

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    Arthur, you know the following:
    t1=s/v+s/v=2s/v
    t2=s/(v+w)+s/(v-w)
    v=2s/t1

    s, t1, t2, and v are all known. All that's left is to do the algebra (and make sure everything is in terms of s, t1, and t2). You have to multiply those fractions in the t2 equation by (v-w)/(v-w) and (v+w)/(v+w) respectively to get a common denominator (v^2-w^2). The rest I'll leave up to you.
     
  8. arthurracoon

    arthurracoon The Cardinal Smiles

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    ok

    so i get:

    t2 = 2vs/(v^2-w^2)

    then i solve for w to get (and i plug in 2s/t1 for v):

    w = sqrt(v^2 - 2vs/t2)

    is this correct? because the online program says its not.
     
  9. nathan

    nathan Moderator Contributor

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    You have to plug stuff into an online program? That sucks. If it asks for a solution involving algebra is it able to discriminate between different ways you can write the answer?

    Yeah I think that answer is right. That's what I got for w, with it simplifying to the form: w=2s/t1*sqrt(1-t1/t2)
    which passes the sanity check of t1=t2 -> w=0.

    Maybe there's something we're missing but everything seems right to me.
     
  10. thirty-two

    thirty-two Cranky Contributor

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    Yeah I was a Sociology/Criminology major in college... sorry Arthur.

    But good luck!
     
  11. arthurracoon

    arthurracoon The Cardinal Smiles

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    yup

    it sucks

    it said i was off by a multiplicative factor....

    stupid masteringphsics.com....
     
  12. arthurracoon

    arthurracoon The Cardinal Smiles

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    i think it plugs in numbers to check

    i entered both forms of the solution (simplified and unsimplified)...wrong both times

    i hate doing physics on a computer...
     
  13. arthurracoon

    arthurracoon The Cardinal Smiles

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    wow...im an idiot.

    s is the round trip distance...not one way...
     
  14. arthurracoon

    arthurracoon The Cardinal Smiles

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    yup...i got it...

    thanks nm132!

    :raccoon:
     
  15. nathan

    nathan Moderator Contributor

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    Me too. I was reading your post about it telling you that you were off my a multiplicative factor and then realized what the issue was. :thumbup:
     

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