this post was submitted on 26 Feb 2024
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@Barbarian@sh.itjust.works's comment is great as a short answer. Below is a longer answer that I've tried to write simply.
Kilograms and pounds both measure mass, how much "stuff" is crammed into an object. It is something that every object has, and it doesn't change depending on where you are.
Weight tells you how heavy it feels to lift an object. This can change on other planets or even on Earth if you climb a mountain.
So if you climb a mountain without losing any mass, technically you will lose weight (but not a lot).
I think most of us were taught in school that pounds measure weight, which is mostly wrong. However, if pounds hypothetically did measure weight, then the person in your post would be technically be able to change their weight in pounds without changing their mass in kilograms (by climbing up a mountain).
Additionally, in some sense, a pound is "a smaller version of a kilogram". You can get a pound by cutting off a part of a kilogram. In comparison, you cannot get a foot by cutting a kilogram. They don't measure the same things.
Hope you get some good sleep soon!
No, pounds in the traditional usage refer to lbf, or weight. If you stand on a scale, it measures the force you're exerting on the scale, which is absolutely distinct from mass because the exact same scale would show a different value on Mt Everest despite you not losing any mass. Every practical use will be measuring lbf. Ie PSI, or pounds per square inch, is clearly referring to force over an area, not mass.
1 lbm weighs 1 lbf on earth, which implies that accelerating a 1lbm object at a rate of 32.2ft/s2 requires 1lbf.
Engineers are the few types of people that actually use lbm and slugs. Sensible ones will prefer to just use metric.
The comment to which you replied is a heavily-simplified version of a previous comment.
I alluded to that in the more-complex first comment. The thing is that the notion of a "pound" was conceived before the distinction between mass and weight was understood.
However, the pound has been legally defined by the United States and a bunch of other countries that use the avoirdupois pound to be a unit of mass since 1959. It's been 65 years.
That's what I said.
As I stated in the more complex comment, I acknowledged that both lbm and lbf exist, but that lbm is the unit both US Customary and British Imperial systems use to define "the" pound. This makes lbf a derived unit in those systems.
So technically, PSI really should be called "pounds-force per square inch".
Actually, the equations of physics in electrical engineering vary more severely with the choice of units than those in other engineering subdisciplines, particularly Maxwell's equations. For that reason, and because exact conversions exist between SI and US customary, I literally always convert US customary or other "weird" units to SI and convert back the SI result if US customary is required. So I basically don't use slugs, lbm (except to weigh myself), or US customary in quantitative work unless I am literally forced to do so like I was in my diff EQ course. I'm just pedantic.
Yes it is very pedantic to refer to a legal definition lol. Realistically, eliminating the idea of lbm entirely would make the entire conversation much more sensible.