Newtons vs. Pounds: Why Do We Use Them?

[alyafey22]

it was really tough to me to understand the relationship between the Newtons and Pounds, not in mathematical term that lb=4.45 N , but I always find problems to understand why do people use it >>> and why Pound does equal approximately half of Newton << I mean what is the first to be found ?? Newtons or Pounds ?

 

[cepheid]

They come from two totally different unit systems. The Newton is the unit of force in the metric (a.k.a. SI) unit system. The pound is the unit of force in the British/Imperial/American (whatever you want to call it) system of units. The Imperial system came first. The metric system came later and it was an attempt to create a new unit system that defined things in a more systematic and useful way.

I don't know what you mean by "why Pound does equal approximately half of Newton." It doesn't. In fact, you just stated above that that 1 lb = 4.45 N.

 

[Lsos]

Yeah I don't think there's some mathematical reason driven by fundamental laws that 1 lb = 4.45 N. Most likely some guy a few hundred years ago decided that the weight of his left shoe will be now called a "pound". Perhaps because his name was "Pound" or perhaps it had some other meaning at the time.

He was probably famous or smart or both, so people listened to him and there you have it, the pound was born.

Then later someone put the left shoe on a metric scale and it happened to weigh .45kg.

 

[uart]

The pound weight can be traced back to the weight of ancient silver pennies needed to make a "moneyer's" pound. The weight of this original silver penny was in turn derived from even older Arabic silver coins which were specified to be minted at a weight of 45 full grown barley grains. So the pound weight was in fact 45*20*12 divide 2 (see note) = 5400 full grown barley grains.

Note. At some point the coin sizes were halved to conserve silver, hence the divide by two.

 

[alyafey22]

The pound weight can be traced back to the weight of ancient silver pennies needed to make a "moneyer's" pound. The weight of this original silver penny was in turn derived from even older Arabic silver coins which were specified to be minted at a weight of 45 full grown barley grains. So the pound weight was in fact 45*20*12 divide 2 (see note) = 5400 full grown barley grains.

Note. At some point the coin sizes were halved to conserve silver, hence the divide by two.

thanks very much that was pretty convincing