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Homework Help: Joules and Kinetic Energy [units wise]

  1. Jan 5, 2009 #1
    K.E is in joules

    joules = 1Nm

    Nm = m/s² . m
    = m²/s²

    therefore

    k.e = 0.5mv²

    m²/s² = kg . m²/s²

    there is an extra kg. I dont see how

    there is the same problem with GPe
    GPE = m gh
    m²/s² = kg . m²/s²

    How can that be. The units of 0.5kgv² need to equal Nm

    Thanks :)
     
  2. jcsd
  3. Jan 5, 2009 #2

    mgb_phys

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    N = kg m s-2 ( from f=ma )

    Energy = Nm = kg m2 s-2
     
  4. Jan 5, 2009 #3
    i was just on my way to delete this post when i realised whay a stupid mistake i'd made.
    F = ma
    N = kg . m/s²
    :blushing:
    cheers :)
     
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