1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

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


    User Avatar
    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?
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook