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Homework Help: Calculating acceleration with slug and lbs

  1. Oct 11, 2012 #1
    1. The problem statement, all variables and given/known data

    What is the acceleration when a 30.0 lb force acts on a 12.2 slug mass?

    2. Relevant equations

    3. The attempt at a solution

    I can't quite figure out the slug thing. I took 12.2 slugs to be 392.5 lb/ft/s2
    Then divided 30 by 392.5 lbs got cancelled out and I'm left with ft/s2 in denominator which the is reversed because we are dividing fractions ??? Is this right? I get 7.6 x 10 -2 ft/s2
    Thanks a million!!!!
    Last edited: Oct 11, 2012
  2. jcsd
  3. Oct 11, 2012 #2
    According to Wikipedia, 1 slug = 1 lbf/ft/s2.
  4. Oct 11, 2012 #3


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    hi tratata! :smile:
    no, you don't need to convert …

    the whole point of using slugs is to keep things simple …

    F = ma works fine if the mass is in slugs and the force is in lb-force :wink:

    from the pf library on slug
    In Europe, a slug is one of many varieties of gastropod mollusc.

    In English-speaking countries, it is a unit of mass, equal to g pounds-mass (i.e., 32.17405 lbm). It is the amount of mass that will accelerate at one foot per second squared when one pound-force is applied.

    It can be thought of as a pound-weight divided by 1 ft/s².

    It is mostly used when "pound" is used to mean a force, and avoids the need of an extra constant in Newton's second law [itex]\mathbf{F}\ =\ m\mathbf{a}[/itex].

    It is a unit in the gravitational foot-pound-second (fps) system.​
  5. Oct 11, 2012 #4
    Hi tiny-tim! Thanks for your response! If a=F/m and I don't need to convert then I divide 12.2 by 30 I get 0.41 - where lbs gets cancelled out and I'm left with ft/s2? Does that seem right? Thanks!!!
  6. Oct 12, 2012 #5


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    hi tratata! :smile:

    (just got up :zzz:)
    wouldn't it be better to divide the force by the mass? :wink:
  7. Oct 14, 2012 #6
    It sure would )))))))
  8. Jun 18, 2013 #7

    hey guys i want to become a scientist and i need lessons
  9. Jun 18, 2013 #8


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    That's what school is for.
  10. Jul 8, 2013 #9


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    I've been using the internet for quite some time. I haven't become old enough for my first high school physics/chemistry class but that doesn't mean the the information isn't out there. Wikipedia is your friend.

    Also this is a good site: https://www.khanacademy.org/science/physics

    And this guy on youtube: https://www.youtube.com/user/DrPhysicsA
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