Yahoo Answers physics section quality is terrible

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Rach3 said:
What to photons have to do with it? I use natural units. It's all-natural. That means no added artifical flavors or pesticides.

Well photons have frequency, photons are energy, energy can be converted into mass, mass cna have units of "lbs". Its a stretch i know but that's all i could think of.
 
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mass can have units of lbs?
 
lbs... as in pounds right? Don't we use pounds for force and mass in the english system?

lbs is pounds right?
 
Yes so I looked it up and they're used for both.
 
No, there are two different units. See http://en.wikipedia.org/wiki/Pound-force.

A pound is in fact a unit of mass, albeit an Imperial British unit, disowned by the British Imperials and taken on by their colony as a symbol of cultural identity (because being American is all about being a colony of the British Empire! Silly non-metric Americans... :rolleyes:). The corresponding unit of force is the "pound-weight", the gravitational force on a pound at sea level, a unit so stupid even Americans won't touch it.
 
Pengwuino said:
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.

Math Is Hard said:
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" :smile: :smile:
 
dav2008 said:
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.
 
Oh yah that slug unit
 
selfAdjoint said:
(snip)acceptable hack in normal circumstances. 1 lb = 2.2 Kg.
(snip)

Wanna run that by again?
 
selfAdjoint said:
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.
 
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.
 
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selfAdjoint said:
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?
 
Rach3 said:
Um, no? :confused:
Any quantity with dimensions [itex][M^a~L^b~T^c][/itex] does (a,b,c integers).
 
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!
 
Rach3 said:
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 [itex]\sqrt{\frac{\hbar c^5}{G}}[/itex] to leave you with [energy].
 
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.
 
dav2008 said:
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.
 
FredGarvin said:
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.