How Do I Convert Pounds to Kilograms?

  • Context: Undergrad 
  • Thread starter Thread starter Hollywood Dave
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Discussion Overview

The discussion revolves around the conversion of pounds to kilograms, addressing the conceptual differences between weight and mass, and the implications of gravitational acceleration in these conversions. Participants explore various methods and formulas for converting between these units, while also questioning common misconceptions related to weight measurement.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Mathematical reasoning

Main Points Raised

  • One participant notes that a pound measures weight (force) while a kilogram measures mass, questioning how to properly convert between the two given their different definitions.
  • Another participant emphasizes that measuring weight in kilograms perpetuates a misconception, suggesting that what is often meant is the weight of a mass in kilograms on Earth.
  • A participant mentions that a spring scale measures weight and a balance measures mass, indicating that practical applications often blur the distinction between the two.
  • One participant seeks to understand the derivation of the commonly used conversion factor of 2.2 kg/lb, expressing a desire for a formula that accounts for gravitational acceleration.
  • Another participant provides a formula for weight in Newtons and explains the conversion from pounds to kilograms using gravitational acceleration and the relationship between pounds and Newtons.
  • A participant shares specific conversion factors, stating that 1 pound equals approximately 0.45359237 kilograms and 1 kilogram equals approximately 2.20462262 pounds, along with examples of conversions.
  • One participant reiterates the need for a formula that accounts for gravitational acceleration in the conversion process, while also suggesting a relationship between force and mass.

Areas of Agreement / Disagreement

Participants express differing views on the conceptual understanding of weight versus mass and how this affects conversion methods. There is no consensus on a single formula or approach to the conversion, as various methods and interpretations are presented.

Contextual Notes

Participants highlight the importance of gravitational acceleration in the conversion process, but there are unresolved questions regarding the derivation of conversion factors and the implications of using them in different contexts.

Who May Find This Useful

This discussion may be useful for individuals interested in the physics of measurement, conversion between units of weight and mass, and the implications of gravitational effects on these conversions.

Hollywood Dave
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A pound being a measure of weight (force)and a kg being a measure of mass - how would I convert lbs. to Kg? If F=ma, Kg would be on the right of the equation and Lb. on the left which I don't think is equal since a lb. takes into consideration the acceleration of gravity and the Kg does not. I can't seem to put together the acceleration part. If I were to set an equation of - w=mg (w=weight)using the slug as the mass in this equation (similar to the m being the Kg in F=ma)would this be going in the right direction? Pounds v.s Kilograms?
 
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YOu are so correct in being bothered about how to convert pounds to kg. When we measure "weight" in kilograms, we are perpetuating a misconception.

What we mean is "the equivalent weight of this number of kilograms on the Earth's surface. Since most people will not go to a place where g is any different, it really doesn't matter on a daily basis.

To convert "kilograms to pounds" you are actually converting "the weight of so many kilograms" to pounds. THe shortcut: take the number of kilograms and multiply by 2.2. This product will be the weight (in pounds) of however many kilograms you have.
 
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Originally posted by Chi Meson
YOu are so correct in being bothered about this. When we measure "weight" in kilograms, we are perpetuating a misconception.
This is an issue that in practice, both systems screw up. A spring-scale measures weight, and a balance measures mass. In practice, neither differentiates between the two.
 
Thanks Chi.
What I am interested in is how do I get to the daily conversion of 2.2 Kg/Lb.? There has to be something or a formula to account for the acceleration of gravity. Can anyone come up with the actual conversion? I have been unable to find anything of the sort.
Hollywood
 
The weight in Newtons: (mass) x (g)

the conversion: one pound of force is exactly 4.448 Newtons.


take your kilograms, multiply by 9.801 m/s^2 (that's "g") then divide by 4.448 Newtons/pound, et voila.

Or, as I mentioned, keep the factor of 9.801/4.448 (that equals 2.203) to go directly from kilograms to pounds. (Remember, if you go to mars, you need to redo this)
 
Thanks Chi Menson!
That will help!

To convert from pounds to kilograms, you can use the following formula:

1 pound = 0.45359237 kilograms

To convert from kilograms to pounds, you can use the following formula:

1 kilogram = 2.20462262 pounds

To convert a specific number of pounds to kilograms, you can multiply the number of pounds by 0.45359237. For example, to convert 20 pounds to kilograms:

20 pounds x 0.45359237 = 9.0718474 kilograms

To convert a specific number of kilograms to pounds, you can multiply the number of kilograms by 2.20462262. For example, to convert 10 kilograms to pounds:

10 kilograms x 2.20462262 = 22.046226 pounds
 
Originally posted by Hollywood Dave
What I am interested in is how do I get to the daily conversion of 2.2 Kg/Lb.? There has to be something or a formula to account for the acceleration of gravity. Can anyone come up with the actual conversion? I have been unable to find anything of the sort.
Hollywood
That's 2.2 lb/kg. And the formula is f=ma. Make two equations and set a=a. Good luck with the pounds to kg conversion.
 
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