Yahoo Answers: Bastion of Stupidity

[BobG]

lbs... as in pounds right? Don't we use pounds for force and mass in the english system?

lbs is pounds right?

No. lbs are force and slugs are mass. If I deduce your species of penguin correctly, you're a slug. It would take about 32 lbs of force to accelerate you at 1 ft/sec^2.

Oh, mercy! I did a search on "penguins" and got this jewel.

At least there was one jewel: "all peguins are homosexual, and they all go to shark heaven"

 

[selfAdjoint]

Yes so I looked it up and they're used for both.

Lbs (from the latin libra) does mean pounds. They are a measure of weight, that is force, and should not strictly be used for mass, but since at the surface of the Earth the acceleration of gravity is approximately constant, it is an acceptable hack in normal circumstances. 1 lb = 2.2 Kg.

The true English system unit of mass is the slug, defind by 1 slug = 1 pound/ g feet per second per second. Where g is the acceleration of gravity, approximately 32 ft/sec^2.

 

[Pengwuino]

Oh yah that slug unit

 

[Bystander]

(snip)acceptable hack in normal circumstances. 1 lb = 2.2 Kg.
(snip)

Wanna run that by again?

 

[dav2008]

Lbs (from the latin libra) does mean pounds. They are a measure of weight, that is force, and should not strictly be used for mass, but since at the surface of the Earth the acceleration of gravity is approximately constant, it is an acceptable hack in normal circumstances. 1 lb = 2.2 Kg.

The true English system unit of mass is the slug, defind by 1 slug = 1 pound/ g feet per second per second. Where g is the acceleration of gravity, approximately 32 ft/sec^2.

That was my initial thought but then I looked it up and it says that the pound can be a unit of mass as well.

 

[Rach3]

A "pound" is a unit of mass, not force, and don't take my word for it, ask NIST. "Pound-weight", or "Pound-force", is the graviational-force equivalent. Any other usage is in violation of federal law as interpreted by NIST.

 

[Rach3]

The true English system unit of mass is the slug, defind by 1 slug = 1 pound/ g feet per second per second. Where g is the acceleration of gravity, approximately 32 ft/sec^2.

Oh, you mean an Imperial slug. I'm more familiar with the metric slug (9.81 kg).

Funny name, "Imperial Slug". The snail who would be king?

 

[Gokul43201]

Um, no?

Any quantity with dimensions $[M^a~L^b~T^c]$ does (a,b,c integers).

 

[Rach3]

That only gets you powers of energy. [Energy] is not the same as [Energy]^3 or 1/[Energy]. There's a great variety - you can have any integral power of energy you want!

 

[Gokul43201]

That only gets you powers of energy. [Energy] is not the same as [Energy]^3 or 1/[Energy]. There's a great variety - you can have any integral power of energy you want!

Once you have some power of [energy] you merely divide by one lesser power of $\sqrt{\frac{\hbar c^5}{G}}$ to leave you with [energy].

 

[Rach3]

That's because G has units of distance^3 / (mass*time^2) = distance/mass = 1/energy^2. If it were made dimensionless, nothing would have any dimension, and the terrorists win.

 

[FredGarvin]

That was my initial thought but then I looked it up and it says that the pound can be a unit of mass as well.

It is a unit of mass, but it is not the base unit. That is the slug. If one uses pounds-mass in calculations, there is always the 32.2 conversion factor that has to be worked in. It's a pain that is really left over from the older folks. They liked the idea that a unit of mass and force were the same numbers. Personally I found it pretty confusing and it took me a while to get it. I prefer the metric system for doing calcs. The only problem is that I have no feel for what a kilogram or a Newton are. Now a pound and a pound is easy.

 

[BobG]

It is a unit of mass, but it is not the base unit. That is the slug. If one uses pounds-mass in calculations, there is always the 32.2 conversion factor that has to be worked in. It's a pain that is really left over from the older folks. They liked the idea that a unit of mass and force were the same numbers. Personally I found it pretty confusing and it took me a while to get it. I prefer the metric system for doing calcs. The only problem is that I have no feel for what a kilogram or a Newton are. Now a pound and a pound is easy.

One Newton is about the weight of an apple.