Dumb question: Is pound a unit of mass or unit of weight? I have trouble with non SI units?

Question

I've always thought that lb was a unit for weight, but then I saw density expressed in ponds per cubic foot and density is mass/ volume which then indicates that lb is a unit of mass. Am I right, is it unit of mass?
Thanks!

I know the difference between mass and weight, and if it is weight, how can lb/foot cubed be used as a unit of density?

Answer 1

From what I remember, it is both the unit for mass and weight.

Additional: Love Nickleback, there's nothing dumb about your question. It's been many years since I have left the science room. During that time, we were taught that mass and weight are interchangeable. So that is why I said the pound can be used for both mass and weight. But after some research (done immediately after answering your question,) I found out that the concept of mass and weight have somewhat changed. And yet, I can now tell you that the pound is still the unit for both mass and weight. All the other answers given here are correct. Please follow the link below to take you to Wikipedia:

Answer 2

You are right, it is a unit of mass. The unit of weight is different (pound weight) but since g is constant for all practical purposes, a pound is also used for weight. Actually what is meant is that the mass of 1 pound experiences a weight of 1 lb.wt.

Same confusion exists for kg too. kg is the unit for mass and the unit for weight is N. A mass of 1 kg will weigh 9.8 N.

Answer 3

It's both! A pound of feathers and a pound of lead still weigh the same, but the MASS per VOLUME is different. If you drop them thru the air, the lead will hit first, if you drop them thru a vacuum, they both should hit at the same time in the same gravity ( same mass ), depending on their shape. No friction interference. While a lb is used in daily life mostly for weight, once physics is applied, it will change. If you accelerate a weight of 1 lb to near light speed, it's apparent mass will increase due to the force applied to accelerate it. It's still reckoned in pounds, but due to force applied, the equation changes to increase the mass.

Answer 4

It is taken as a unit of mass and weight but in DIFFERENT unit systems.
If you take at a force(weight) the mass in that system is expressed in slugs(as far as I remember) m= weight/g where g is approx=
32feet/s^2.
If you take it as a mass you are in a
system simil to the SI and the unit of force is F=mg(I don´t recall any name for it)

Answer 5

A 'pound' is strictly speaking a unit of mass.
The corresponding unit of weight is actually called a 'pound weight'. For this reason we often sloppily talk about a weight of one pound. We ought really to talk about a weight of one pound weight!

Answer 6

Pounds is a unit of measure for force. It is a unit of force, but newtons are more commonly used in physics. Pounds per square inch is a measure of pressure.

Answer 7

It can be both. There are two systems. If a pound is mass then weight is poundel. If pound is weight then mass is slug. To find.

Answer 8

A pound is a unit of weight. It is the product of mass and acceleration due to Earth's gravity.

Answer 9

Normally a unit of weight in the system where mass is called a slug (~32.2 lb weight on earth's surface).

It is less often a unit of mass in a system where the poundal (~1/32.2 lb) is the unit of force.

It's only easy for those brought up on it--(old codgers like me!)

Answer 10

pounds are units of weight (mass * force). It is sometimes used interchangably with mass, but it is not mass. Mass is a constant no matter what force is being exerted on it (e.g. gravity). But weight has to do with both mass and force.