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Homework Help: Unit conversion problems

  1. Mar 8, 2006 #1
    I have 3 unit conversions and they are not coming out right... what am I doing wrong if you can spot it:
    1)1.64ly/min to SI Units:
    1144.6W/m^2 but how do you get it with just the oringinal SI units...

    2)2.3E27carats/parsec^3 to SI:
    2.3E27carats/parsec^3 * (1kg/.0002carats) *( 1 parsec^3/2.938e49 m^3) = 3.91E-19 but is nothing like what google says !

    3)642 furlongs per fortnight to SI:
    642 furlongs/fortnight * (201.2m/1furlong)*(1/[24*60*60])*(201.2m/1furlong)=.107m/s?
  2. jcsd
  3. Mar 8, 2006 #2


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    Gold Member

    Wait, light years/min??? That's a unit of velocity and W/m^2 is a unit of intensity.
  4. Mar 8, 2006 #3
  5. Mar 9, 2006 #4
    You want the units to be basic SI-units? Well, Watt is J/s and Joule is Nm and Newton is kg m/s^2.

    You calculated the second one wrong. I got 1.566*10^(-26) kg/m^3. Pay attention to what you do when you change units. Remember that 1 carat = 0.0002 kg, not 1kg = 0.0002 carat.
  6. Mar 10, 2006 #5
    That's just one day, not a fortnight.

    And why twice 201.2m/1 furlong?
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