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Pound Force / Pound Mass Question

  1. Sep 5, 2010 #1
    Also an answer to this question would be great:
    "It takes 32.174 pounds force (lbf) to accelerate one pound mass (lbm) one foot per second per second (ft/s^2)

    Correct?"


    Thanks
     
    Last edited: Sep 5, 2010
  2. jcsd
  3. Sep 5, 2010 #2

    PhanthomJay

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    That is not correct. The Imperial/British/USA system of measure, whatever you call it, is confusing. A one pound-mass weighs 1 pound on Planet Earth. It is very confusing in Physics to use the pound-mass term. Instead, always use the 'slug' for mass if using this system. 1 slug weighs about 32 pounds on planet earth. One pound of force will accelerate 1 slug at the rate of 1ft/sec^2. I leave it to you to determine how many pounds of force will accelerate a one pound-mass at 1ft/sec^2, if you dare (it's a lot less than 32 pounds force to do so).
     
  4. Sep 5, 2010 #3
    Goodness... ok.
    I only use pound force and pound mass because my professor uses them.

    Thanks!
     
  5. Sep 5, 2010 #4

    PhanthomJay

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    That's unfortunate in my estimation. When using, for example, F=ma, if you want F in pounds of force and 'a' in ft/sec^2, you'd better be using slugs for the mass unit, or you'll get all messed up.
     
  6. Sep 5, 2010 #5
    I agree. I can understand slugs well because I can relate them to kgs... but throwing lbm into the mix is just overkill.
     
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