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r2k-in-the-vortex t1_ja9wooh wrote

Reply to comment by breckenridgeback in ELI5 how pounds can be converted to kg by cheeseunused

That is a completely different unit, with a completely different abbreviation of lbf. Pound-force is defined as: "weight of one pound"

Pound has abbreviation of lb, it's a unit of mass and is equal to 0.45359237kg

You cannot treat pound as unit of force, because it isn't one. Same as you can't treat pound as unit of torque or unit of energy. Pound-force, pound-foot and foot-pound are all completely different units of completely different quantities and they are definitely not the same unit as pound.

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breckenridgeback t1_ja9znac wrote

It is, formally speaking, a different unit. But for our purposes here on the Earth, where the vast majority of practical use of the units is conducted, the two are proportional and that proportionality is constant enough for the difference not to matter.

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r2k-in-the-vortex t1_jaa1top wrote

If you can't tell a difference between force and mass you might as well not bother measuring anything and just eyeball it.

And the difference of how much a pound weighs varies significantly, at poles its half a percent more than on equator. That's a lot, half a percent makes a difference between a buy and a sell.

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