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Lb/f to kn/m and not consistent

  1. Jun 3, 2013 #1
    I'm trying to convert lb/f to kn/m.
    A concrete has weight of 23.54 kilonewton/cubic meter which is equal to 150 pounds per cubic feet.

    For a beam with the following dimensions
    width = 0.3m = 0.84 feet
    depth = 0.5m = 1.9685 feet

    for the beam weight per meter in metric, it is 23.54*0.3*0.5=3.531 kn/m
    for the beam weight per foot in english, it is 150*0.98*1.96=290.62 lb/foot

    But if I convert 290.62 lb/foot to kn/m. I don't get 3.531kn/m but 4.240181 kn/m
    here's the calculation

    290.62 lb/f * 3.28 f/m * 1kn/224.8lb = 4.24 kn/m

    why not 3.531 kn/m??

    Note this is not a homework. Thanks.
  2. jcsd
  3. Jun 3, 2013 #2
    I didn't check the calculation, but I noticed you wrote 0.84 feet for the width but used 0.98 feet in a calculation a few lines down. Maybe that is where the error lies?
  4. Jun 4, 2013 #3


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    I don't know where you got your meter and feet conversions from, but they are in error.

    1 meter = 39.37 in. = 3.2808 ft.

    1 foot = .305 m
  5. Jun 4, 2013 #4
    i got the error. It's formula in my excel which uses 0.6m instead of 0.5m. Anyway, thanks
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