Pound Force / Pound Mass Question

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Discussion Overview

The discussion revolves around the use of pound force (lbf) and pound mass (lbm) in physics, particularly in the context of acceleration and the confusion surrounding these units in the Imperial system. Participants explore the implications of using these units in calculations related to force and mass.

Discussion Character

  • Debate/contested
  • Technical explanation

Main Points Raised

  • One participant questions the statement that it takes 32.174 pounds force to accelerate one pound mass one foot per second per second, suggesting it is incorrect.
  • Another participant argues that the term pound-mass is confusing and recommends using slugs for mass instead, noting that one slug weighs about 32 pounds on Earth.
  • A participant expresses reliance on pound force and pound mass due to their professor's usage, indicating a lack of familiarity with alternative units.
  • One participant warns that using pound mass in calculations with F=ma can lead to errors unless slugs are used for mass, emphasizing the importance of unit consistency.
  • Another participant agrees with the confusion surrounding lbm, stating that they find slugs easier to understand as they can relate them to kilograms.

Areas of Agreement / Disagreement

Participants express disagreement regarding the appropriateness and clarity of using pound mass in calculations. There is no consensus on the best unit to use, as some advocate for slugs while others continue to use pound mass.

Contextual Notes

The discussion highlights the potential for confusion in the Imperial system of measurement, particularly regarding the definitions and relationships between pound force, pound mass, and slugs. The implications of these units on calculations are not fully resolved.

dillonmhudson
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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
 
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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).
 
Goodness... ok.
I only use pound force and pound mass because my professor uses them.

Thanks!
 
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.
 
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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