Since pounds are a measurement of force and kilograms are a unit of mass how is it possible to freely convert between the two measurements?
In: Mathematics
It’s assumed that were using standard earth gravity (acceleration is 9.8 m/s^2 or 32.2 ft/s^2), it works most of the time. In fact a lot of basic scales measure kg from the force anyway. Newtons second law (F=ma) is used to convert from mass to force.
It goes kg (SI mass) -> N (SI force) -> lbf (US force)
Id also like to clarify pounds force (lbf) and pounds mass (lbm). pounds mass is an actual unit, but it falls under the same category as stuff like furlong. It’s technically a thing, but it isn’t used, US customary doesn’t use mass as a standard measurement like metric, it uses weight. Here’s a list of all the places i’ve used lbm.
1) In my metrology classes learning of it’s existance
2) getting problems wrong for assuming pounds mass instead of pounds force
Edit: added some more detail.
Edit 2: added more detail on conversion and pound mass
The pound is both a unit of mass and a unit of force. Same word, two different definitions in this sense.
Pound is used both as unit of mass and a unit of force.
In the metric system there are two different SI units for this Kilogram and Newton, but the American system uses the same name for both units.
Sometimes the American Newton equivalent is called pound-force to make it more clear what is meant, but usually it is just pound.
Obviously having two different things with the same name can be very confusing.
Usually a pound has the force of a mass of one pound being pulled down by gravity on the earth surface.
This means that if you are anywhere but on the surface the a pound of mass has something other than a pound of force of gravitational acceleration and even here on earth actual surface gravity can vary a lot from 9.780 N/kg at the equator to 9.832 N/kg at the poles for example.
However anyone who actually cares for stuff like that with any amount of accuracy uses SI units anyway.
Pounds are just a convention every day way to convey to people familiar with the weight of 1 pound, how much force is exerted in very rough terms.
With SI units you have all these advantages like 1 N/kg = 1 m/s² and really anyone who cares about the amount of acceleration equal to one 1 pound per pound wouldn’t use units like pounds for either mass or force anyway.
(One pound per pound is 71 billion furlongs per fortnight squared in American units in case you were wondering.)
By itself, a pound is a unit of mass. It can be used to measure pressure, but if it is, it’s pounds per a unit of measurement, such as a square inch (PSI). When interpreted as a unit of mass, it can freely be converted into other units of mass, such as a kilogram, by figuring out the ratio between them, i.e. 1 kilogram=approximately 2.2 pounds.
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