The textbook is incomplete. One of the advantages of SI is that it clarifies the distinction between mass and force especially weight. In the old British Imperial system there are several options:. It's the failure to state this that leads to the confusion. For most practical cases, a pound mass and a pound weight define the same amount of stuff on the surface of the earth. There seems to be some confusion here.
In the English or American system the "official" measure of mass is the slug. Turns out that And, as someone said, at "standard" gravity 1 lbm exerts 1 lbf on its support its weight. If you are going to do any significant calculations, it's best, in my opinion, to get rid of all lbm designations and convert everything to slugs.
The force required to accelerate 1 lbm In this case, it is in units of slugs. Know the base units of the unit system you are working in for ANY final solution to be applied appropriately. Both forms are correct! Essentially, 1 , 2 and 3 are all dividing by Know the base units of your system, lbf will always be an ambiguity problem as long as it exists in its current symbolic form. I'd suggest adopting sdl for 2 lbf with unit slug , the ambiguity of pound is an unusual punishment lb, lbs, lbm, lbf, lbf Absolutely, yes you can.
In fact, the mass of a slug is derived from the acceleration due to gravity. I know it is the standard unit for mass and so is lbm. Once you understand this concept well you can go on to familiarize yourself to using slugs. Looking at the last two points above, it is obvious that the newton is very different that the lbf. In the SI system. When you weigh sometime you are measuring a force, yet in SI we record this force in terms of mass kg.
Why we can not create a system that make sense is beyond me. The confusion comes from the English system, we should not ask what is your weight, but what is your mass. Of course this is ridiculous. The confusion comes from an overgeneralization, i. Personally, I think the guy who came up with the pound mass lbm was dyslexic.
What I think he really wanted to do was state that;. This means that lbm is not really a mass unit, but a mass gravitational constant unit which is ridiculous so when you multiply lbm by an acceleration you have to divide out the gravitational constant before you can obtain a force. Other than by mistake why would anyone come up with such a unit???? How many slug in 1 pound mass? The answer is 0. Note that rounding errors may occur, so always check the results.
Use this page to learn how to convert between slugs and pound mass. Type in your own numbers in the form to convert the units! There is the metric which is 50kg. The other tons are always 20 Cwt. The US hundredweight is lb avdp or Which obviously eventually gives rise to the short ton of lb US and the long ton lb UK and obviously the metric ton which is actually the tonne which is lb avdp. The French with the SI had to confuse everything! Your email address will not be published. Subscibe to ProjectEngineer.
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