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B Why is a newton of force .225 pounds?

  1. Sep 9, 2017 #1
    General physics question regarding force and gravity. Hypothetically speaking if every piece of mass weighed double. If something that weighed 1 Pound is now 2 pounds. If you weigh 100 pounds now you weigh 200 pounds . Assume gravity is still 9.8ms/sq. and you never experience gravity any other way Would it then be accepted as the new normal of force. Now a newton would be equal to .45 pounds force instead of .225. In order to satisfy newtons law of mass x acceleration = force would then mean that everything would require double the amount of force to accelerate at any rate. A newton would still be a newton but the actuaL real measurable force would be double. So my question is why is the actual force for a newton what it is. ? Why is 1 newton .224 pound force? Why not 3 pound force , why not 5 why not 100 pound force? I understand however this number increases proportionally it would also increase the actual force for any rate of acceleration on any mass proportionally. So why is the actual real force what it is ? It could be any amount of force and as long as it is satisfied by mass x acceleration it would mean that the force for everything else would be proportionally increased. So basically I am asking why the force to accelerate 1 kg 1 m/s sq which is 1 n of force is .225 pounds why not any other number. (And yes I understand that it would effect the force required to accelerate any mass at any rate of acceleration )
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  3. Sep 9, 2017 #2


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    The definition of pound is from ancient languages and (speculative) refers to a weight that will stretch a rope a certain amount. So it is not a modern definition defined by physics. (see definition n.1 in http://www.etymonline.com/index.php?term=pound )

    Speculating on how the historical definition of "pound" would change is open to too much debate. Whatever amount of force it would mean, it's conversion to newtons would be determined by the new ratio of the new definition of a "pound" of force to the standard definition of a newton of force.
  4. Sep 9, 2017 #3


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  5. Sep 10, 2017 #4


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    How would you reconcile those two statements?
  6. Sep 10, 2017 #5


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    As @jedishrfu points out, the pound-force and the newton are both units of force that were originally defined in totally independent ways. It is a simple matter of measured fact that the one definition yields a quantity that is 0.225 times the other.

    Certainly the two units could have been defined differently and the ratio could have been different.
    Last edited: Sep 10, 2017
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