Mass explanation: I’ve always been told that mass was not the same as weight, and that grams are the metric unit of mass. But grams are a measurement of weight, so am I stupid, was it was explained to me wrong, or is science just not make sense?
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This actually came up yesterday.
Here is a slightly editted version of my answer from yesterda.
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In physics:
* Mass is basically how much matter something contains. (Its not exactly that but it is kinda like that.)
* Weight is the force of gravity on that mass. Technically measured in Newtons, (but you can measure it in ‘how much mass would you need to generate this force near the surface of the Earth from its weight’.)
* The weight measurement on a scale is the force needed to hold up the object being measured.
In common, everyday language and scenarios, if you are near the surface of the Earth, and neither you nor the scales are accelerating, then those 3 things are essentially all the same, because they are designed to try to measure the same thing. We calibrate the scale to not show ‘Newtons’, but instead show ‘the amount of mass needed to produce a weight force of this magnitude’.
So if you put a 1kg mass on a scales, then a weight force pressed down on the scales. A physicist would measure the force in Newton’s, but for our every-day use, the readout is calibrated to say “This is as heavy as a stationary object with a mass of 1kg near the surface of the Earth would be.” (which, since you *are* near the surface of the Earth, means that it *is* 1kg of mass).
(If you happen to be not near the surface of the Earth, or and using scales that are accelearating, then these 3 concepts can become separate, and you probably need physics calculations to be able to use them in any useful way. Your scales will display the wrong mass on the Moon, or in an elevator, for instance.)
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