# Physics Question

Discussion in 'After Hours Lounge (Off Topic)' started by Mark Fitzsimmons, May 28, 2003.

1. ### Mark Fitzsimmons Supporting Actor

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My physics teacher claims that a pound of feathers weighs more than a pound of nails. I think that they both weigh a pound. . .

Can any physics gurus shine any light on this?

2. ### Andrew_Sch Cinematographer

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No...because it's bogus.

3. ### Paul McElligott Cinematographer

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Absolutely bogus. A pound is a pound.

4. ### Hunter P Screenwriter

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I suppose it is possible since a pound is the measure of gravitational force on an object. If the nails were on the Moon and the feathers on the Earth then the statement would be true.

If they are side by side then there is no way that one is heavier.

5. ### Mark Fitzsimmons Supporting Actor

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Even if they are side by side here on earth, so under the same amount of gravity. He still claims the feathers weigh more.

6. ### D. Scott MacDonald Supporting Actor

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A pound is a unit or weight. Hence, a pound of anything is equal to a pound of anything else (at least in weight). If one weighed more than the other, then one of them wouldn't be a pound.

7. ### Jay Heyl Stunt Coordinator

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I've heard it said that a pound of feathers weighs more than a pound of gold. I've never heard nails mentioned in relation to feathers.

The feathers/gold thing is a trick question. Feathers, like most common substances, are weighed using the avoirdupois system of weights, in which a pound contains 16 ounces. Gold, and most other precious metals, is typically weighed using the troy system, in which a pound contains 12 ounces. (Apologies to the metrically-enabled for whom I'm sure this makes even less sense than to those of us encumbered by an antiquated system of measure.)

9. ### Christ Reynolds Producer

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wait, this guy is your physics TEACHER? yikes.

CJ

10. ### Jagan Seshadri Supporting Actor

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Weight is different than mass.

A pound is a force unit that depends on the gravitational (and other) acceleration. Mass (i.e. a kilogram) is independent of accelerations, and is more a measure of 'matter'.

(Think about this: when you're in an elevator, your weight changes as you accelerate upwards or downwards, even though your mass remains constant.)

Assuming that the pound of feathers and the pound of nails are weighed under the same gravitational (and other) acceleration, then they both 'weigh' the same.

-JNS

11. ### Mark Fitzsimmons Supporting Actor

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As aforementioned, they are under the same force of gravity.

12. ### Jagan Seshadri Supporting Actor

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Well, is one being weighed in an accelerating frame of reference such as an....elevator? That would change things.

-JNS

13. ### Mark Fitzsimmons Supporting Actor

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No.

14. ### Yee-Ming Producer

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I vaguely recall some form of trick question based on this, the twist being that a bag of a pound of feathers contained more air than a bag of a pound of nails would, and hence would be marginally heavier. But that's a fallacious reason anyway.

15. ### Jagan Seshadri Supporting Actor

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The problem with the air-in-the-bag argument is that the air contributes no weight since it is neutrally buoyant in the air outside the bag.

Either your Physics teacher made a mistake or the answer to this is going to be corny!

-JNS

16. ### Adam Bluhm Supporting Actor

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I hope to hear this answer.

17. ### Glenn Overholt Producer

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It is probably true. A pound of nails doesn't weigh 16 ounces, as it is on a different scale, just like gold is.

You should look up how nails are weighed, legally. I'm not sure, but an 8d nail can only have a certain number until it reaches a 'nail's pound'. Maybe you can ask a carpenter.

Glenn

18. ### Kirk Gunn Screenwriter

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So this is really a Standards question and not a physics inquiry ? Guess it's good for a teacher to bring this up since not adhering to proper standards can really muck things up (original Hubble Telescope mirror for example).

19. ### BrianW Cinematographer

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20. ### Jay H Producer

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African or European feathers?

Jay