How fast does light travel in 1 ft?

  1. Aug 7, 2007 #1
    Hello everyone,

    I was wondering if anyone could help solve my problem...

    ...How much time in seconds (or milleseconds) would light travel in 1ft? (assuming that it was traveling in a vacuum.)

    I spent 2 and a half hours yesterday trying to solve this problem, but without much luck. I remember back in school, I would know how to do this kind of stuff, but now...well, you know.

    If anyone knows the answer to this problem (and if possible, a formula), I would much apreciate it.
     
  2. jcsd
  3. Aug 7, 2007 #2
    speed = distance / time. Use google calculator. Welcome to PF.
     
  4. Aug 7, 2007 #3

    Gokul43201

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    How much time to cover 300,000,000 meters (that's about 1,000,000,000 ft)? So, how much time to cover 1 ft?
     
  5. Aug 8, 2007 #4

    Wow, I don't believe how I could forget something so simple.

    Thanks anyways for reminding me.
     
  6. Aug 8, 2007 #5

    robphy

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    um... wait, gimme just a .... o:)
     
  7. Aug 8, 2007 #6
    ...and a teeny, tiny bit more. :tongue2:
     
  8. Aug 8, 2007 #7

    mgb_phys

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    Light travels at 1 foot / atto-fortnight, everyone knows that.
     
  9. Aug 8, 2007 #8
    You are a nerd among nerds :rofl:
     
  10. Aug 8, 2007 #9

    mgb_phys

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    No, a real nerd uses c = 1.8 terafurlongs per fortnight
     
  11. Aug 8, 2007 #10

    HallsofIvy

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    And watch them ponys run!
     
  12. Aug 8, 2007 #11

    Dick

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    Um, what's that in planck units?
     
  13. Aug 8, 2007 #12

    mgb_phys

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    That would be a good homework question, what is planck's constant in the furlong/firkin/fortnight system.
     
  14. Aug 8, 2007 #13

    Dick

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    Mines a trick question. In planck units c=1, hbar=1 and G=1. Yours is harder. What's the mass unit in the firkin system? Stones, right?
     
  15. Aug 9, 2007 #14

    robphy

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    Using dimensional analysis,
    h is in Joule-seconds or kg*(m/s)^2*s = kg*m^2/s

    Although http://en.wikipedia.org/wiki/FFF_System says that firkin is a mass,
    according to http://en.wikipedia.org/wiki/Firkin and google, firkin is a volume: http://www.google.com/search?q=firkin+in+m^3 .
    However, since it is used with water (whose density is about 1000 kg/m^3), we have an expression for the mass in kg of a firkin of water http://www.google.com/search?q=kg+in+firkin*(1000+kg/m^3)

    So, since google has a problem with numerical constants in the unit conversion,
    http://www.google.com/search?q=h/1000+in+(firkin)*(kg/m^3)*furlong^2/fortnight

    h / 1 000 = 4.8405995 × 10-34 (firkin * (kg / (m^3)) * (furlong^2)) / fortnight


    or
    h = 4.8405995 × 10^(-34) (firkin of water) * (furlong^2) / fortnight


    (FYI: http://www.google.com/search?q=c+in+furlongs+per+fortnight yields
    the speed of light = 1.8026175 × 10^12 furlongs per fortnight)
     
    Last edited: Aug 9, 2007
  16. Aug 9, 2007 #15

    mgb_phys

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