Like the title. How are we able to convert pounds, which are a unit of force, to kg which is a unit of mass, using a simple scale factor. How are electronic scales able to give us a unit of mass when they measure by using the force enacted on the scale by gravity because all they are doing is using a conversion factor between pounds and kg that shouldn’t exist
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Pounds are a unit of force, while kilograms are a measure of mass, true. However, on Earth they are interchangeable because the difference between a measure of force and a measure of mass in this case is gravity. The pound takes into account gravity, and mass does not.
However, so long as they are in the same gravitational field, they are effectively the same unit. You can think of it as adding gravity to kilograms to make it a force or removing gravity from the pound to make it a unit of mass. Either way, you end up with comparable results if the gravity is the same.
It also does not matter what gravity it is, on the Moon, Earth, Jupiter, or a neutron star. So long as the gravity for both is the same, kilograms are effectively a unit of force and pounds a unit of mass.
Pounds are a unit of force, while kilograms are a measure of mass, true. However, on Earth they are interchangeable because the difference between a measure of force and a measure of mass in this case is gravity. The pound takes into account gravity, and mass does not.
However, so long as they are in the same gravitational field, they are effectively the same unit. You can think of it as adding gravity to kilograms to make it a force or removing gravity from the pound to make it a unit of mass. Either way, you end up with comparable results if the gravity is the same.
It also does not matter what gravity it is, on the Moon, Earth, Jupiter, or a neutron star. So long as the gravity for both is the same, kilograms are effectively a unit of force and pounds a unit of mass.
Pounds of mass and pounds of force are both named pounds. 1 pound of mass has a weight of 1 pound of force while on Earth. We usually don’t distinguish between them, but as long as you’re on Earth it doesn’t really matter.
Pounds of mass and pounds of force are both named pounds. 1 pound of mass has a weight of 1 pound of force while on Earth. We usually don’t distinguish between them, but as long as you’re on Earth it doesn’t really matter.
Quick way of doing it in your head: add 10% and then double it. It’s not precise but pretty close.
Edit: sorry, it’s the other way round. Lbs->kg would be dividing by 2 and substracting 10%
Check: 1lbs is 0.453592…kg
1/2 = 0.5
0.5 – 0.05 = 0.45 –> off by about 3.592g
The other way round: 1kg is 2.2046…lbs
1*2 = 2
2 + 0.2 = 2.2 –> off by about 0.0046lbs
Gravity applies a practically constant force on you at earths surface. If you don’t go deeeep underground or really high above earth, 9.8 meters per second is a pretty good number.
So, on earth’s surface, one kg of mass is approximately 2.2 lbs of weight and 9.8 newtons.
Go somewhere where gravity is half as much as ours and the same kg weighs 1.1 lbs and 4.9 newtons.
Force is only worthwhile as a PROXY for mass when measuring on equal gravity. So, for most experiments on a single planet with a strong gravity, it’s fine to use force for calculations.
Someone here says they’re 400 lbs and you may be able to picture their fitness level. Someone on the sun’s gravity weighs 400 lbs and they’re the size of a baby. A 100 kg person weighs differently on the sun too, 30 times more, but they would still be 100kg. And dead, but this is a thought experiment.
When you’ve got multiple gravitational fields to think about, knowing the mass of an object makes your life way easier. Even in the US, physicists use metric for this very reason.
How did I do for simplicity?
Gravity applies a practically constant force on you at earths surface. If you don’t go deeeep underground or really high above earth, 9.8 meters per second is a pretty good number.
So, on earth’s surface, one kg of mass is approximately 2.2 lbs of weight and 9.8 newtons.
Go somewhere where gravity is half as much as ours and the same kg weighs 1.1 lbs and 4.9 newtons.
Force is only worthwhile as a PROXY for mass when measuring on equal gravity. So, for most experiments on a single planet with a strong gravity, it’s fine to use force for calculations.
Someone here says they’re 400 lbs and you may be able to picture their fitness level. Someone on the sun’s gravity weighs 400 lbs and they’re the size of a baby. A 100 kg person weighs differently on the sun too, 30 times more, but they would still be 100kg. And dead, but this is a thought experiment.
When you’ve got multiple gravitational fields to think about, knowing the mass of an object makes your life way easier. Even in the US, physicists use metric for this very reason.
How did I do for simplicity?
Pound or lb is a unit of mass defined as 0.45359237kg,
Pound-force or lbf is a different unit defined as weight of one pound. That is of course not a fixed quantity, but depends on location, Earth’s gravity is not exactly the same everywhere.
Quick way of doing it in your head: add 10% and then double it. It’s not precise but pretty close.
Edit: sorry, it’s the other way round. Lbs->kg would be dividing by 2 and substracting 10%
Check: 1lbs is 0.453592…kg
1/2 = 0.5
0.5 – 0.05 = 0.45 –> off by about 3.592g
The other way round: 1kg is 2.2046…lbs
1*2 = 2
2 + 0.2 = 2.2 –> off by about 0.0046lbs
Pound or lb is a unit of mass defined as 0.45359237kg,
Pound-force or lbf is a different unit defined as weight of one pound. That is of course not a fixed quantity, but depends on location, Earth’s gravity is not exactly the same everywhere.
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