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?
In: 140
No, grams are a measurement of *mass*, not weight. Weight is the force of gravity *acting* on a mass, such that F=mg (where g is the acceleration due to gravity, and is approximately 9.81 m/s^2 at sea level ). That is in the unit of Newtons.
The thing is though that g is only really variable by non-negligible amounts at very large distances, so for most purposes we just treat g as the above value on Earth. And if g is approximately constant for most uses, the main relevant variable in most cases is mass.
So the short version is that they are *technically* two different things, but for most purposes here on earth the main thing that changes with weight is mass, so sometimes people just sort of equate the two.
Answer:
mass is how much stuff you have (how many atoms or molecules)
weight is how ‘attractive’ stuff is to the closet huge thing (planet, natural satellite, star) this is determined by gravity (of the nearest huge thing).
on Earth mass is can stand in for weight and vice-versa.
this is because 10kg of stuff is being acted on by earth so the mass and weight can have the same name.
on the moon 1kg of gold has a mass of 1kg but a weight one sixth as much. (IIRC)
on Mars 1kg of gold is how many atoms of gold you have but it weighs 0.75 its weight on earth.
Kinda like inflation a dime is a dime, a dollar is a dollar, (mass) but a dime used to buy 10 candies… won’t buy anything in the current gravity (weight).
There are two distinct notions of mass.
“Inertial mass” is a measure of how hard it is to change the current speed of the object. (A lorry has more inertial mass than a car; it’s harder to slow it down when it’s moving).
The other notion is “gravitational mass” – how hard it is to move an object against gravity. (A lorry has more gravitational mass than a car – it’s harder to lift it up).
The actual effort required to “lift” an object with gravitational mass through a particular gravitational field is called “weight”. (A lorry has more weight on earth than on the moon. It has the same gravitational mass, but the gravity is weaker on the moon so it’s easier to lift).
Essentially, gravitational mass is an *intrinsic property of just the object*. Weight is this intrinsic property of the object *combined with the strength of the gravity it’s sitting in*.
Interestingly, the numerical value of the inertial and gravitational masses is exactly the same, and we don’t really know why. In Einstein’s general relativity, their equivalence is taken as a postulate called “the principle of equivalence”. People have proposed some theories (e.g. string theory) that allow you to derive the equivalence from more fundamental axioms, but we don’t know the real answer for sure yet.
Grams are a measurement of mass, not weight. The measurements of weight are pounds or newtons. Technically, people shouldn’t be using grams to describe the weight of things. But practically speaking, it works as a measurement of weight since when you’re on earth, 1g of mass will always have a weight of 0.002lb. So people will know how much weight you’re talking about. But if you were to go to the moon, 1 gram of mass will weigh much less due to there being less gravity on the moon (0.0003lb), but it will still have 1g of mass.
Basically mass and weight are fundamentally different properties. Mass is a property of things that describes how difficult it is to move, and it doesn’t change no matter where that thing is. Weight is the force of gravity something exerts, and it is dependent on where you are. On the moon your weight is very small, on earth it’s bigger, on the sun it’s even bigger than that. But no matter where you are, your mass will always be the same.
Mass is matter. It does not care if it in grams, pounds, or whatever gravitational force is holding it, or arbitrary force we invent.
What I am trying to get at is matter is restless mass, which is energy, which doesn’t rest.
A photon is massless energy, always moving, at a measurable speed.
Quantum physics gets deeper into this, but it’s not eli5 material.
Photons have no mass, but energy. There was a guy who wrote a paper in 1915…
Mass and weight are not the same. However since we live in an environment where gravity is pretty much the same everywhere, any measure of mass implies a certain weight, and any weight implies a certain mass. So, we use units for mass and weight interchangeability.
A gram is a unit of mass, but if you know something has a gram of mass, you know it has a weight of 0.0098 Newtons.
Helium balloon does not have negative mass but it has negative weight. Mass is independent of gravity while weight is related to elements around.
Grams are not a measurement of weight. Grams are a measurement of mass, and mass simply means how much matter is in something. Weight, on the other hand, measures how much gravity is pulling on an object with mass.
So, something with a mass of 1 kilogram has a mass of 1 kilogram whether it is on Earth, on the moon, or in the vacuum of space. Because the amount of matter in that thing does not change, regardless of where it is. But an object that weighs 1 pound on Earth will only weigh 1/6th of a pound on the Moon, but will weigh nothing in space, because Earth has stronger gravity than the Moon, while there is practically no gravity in the void of space.
To summarize, mass is an inherent property of something, but weight depends on the object’s location in the universe (though you do use mass to calculate weight). Mass remains constant, but weight can change (in fact, your weight slightly fluctuates throughout the day as the Moon rotates around the Earth, slightly changing how much gravity is pulling on you). And an object made of matter can have zero weight (if it experiences no gravity) but can NEVER have zero mass.
Wait… there is something to what you said…
Metric is based on a cubic centimeter of water, at 1 degree C. If the water is 100% water, then its MASS is 1 gram. The WEIGHT of that cubic centimeter at Earth sea level is also 1 gram.
So when someone talks about grams, it can be either weight or mass.
Mass is just the product of volume and density, so a representation of the concentration of atoms in a defined space. Weight is the force, due to gravity, this product experiences.
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