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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Grams are not the measurement of weight. The measurements of weight is Newton. While your mass is 70kg, your weight is 700N. It’s about simplification.
Not the same. Grams measures mass and newtons measure force, being weight a force. What you are referring to is using grams-force as a technical weight unit, which is legit. Usually people just say grams to simplify.
A scale does not measure mass, but the force excerted on the mass in a gravitational field. It is calibrated so you can immediatly read of the mass in grams or kg (or lb if you are siding with the empire), but if you would use a scale from earth (or Jupiter) on the moon (or anywhere else), you would get a “wrong” mass reading.
Mass and weight are the same only on earth because gravity is the most eli5 way.
But pretend that car or bowl of soup is now on the moon. The mass is the same but the weight is less.
Mass is a property, it describes an object. Mass is how much stuff makes up an object.
Weight is a force, it tells you how hard an object is pulled towards the earth, or whatever planet/object you are measuring the weight on.
Weight is related to mass, it is actually the mass multiplied acceleration due to gravity (W = mg).
It’s confusing because people talk about their weight but us units for mass. I’m sure it wouldn’t work out well if you asked someone how massive they are though!
Mass means the **amount of stuff**.
Weight means **the force with which that stuff is being pulled with towards the planet**.
When a bit of Elon musk’s rocket takes off on the earth and lands on mars (presuming the part wasn’t expended and stayed the same), its mass – the amount of stuff – you’re basically counting the amount of stuff in the atoms it is composed of – will remain the same. Its weight on Mars, however, eg the force with which the rocket part and the planet pull on each other, will have changed from what it was back on earth, because Mars gravity is different.
At an even more basic level, the reason for that gravitational pull planets have on us is the mass of the planet. The force two bodies exert on each other depends on their mass. Of course the mass of a planet is so, so so much bigger than that of a small object like a rocket, that the impact the rocket has on the planet is approximately nil, while the impact of the planet on the rocket is pretty significant.
Mass is a measure of the amount of an object. Weight is the measure of force acting on an object due to gravity. Something that is 10 grams on earth will still be 10 grams on the moon but the weight will be different at these two locations. We can relate weight to mass on the earth because we know the gravitational force.
How does a scale that measures in grams work then? How does it remove the gravitational effect if it’s under the same influence?
Mass is a measure of how much “stuff” there is. Everything is made from protons and neutrons and they the more of them an object has the more mass it has. (Approximately, I am igboring electrons (very light) and energy, because Einstein told us energy is also mass)
The more mass something has, the harder it is to change the objects velocity. It’s much easier to push a 1 kg rock than a 1000 kg rock. This resistence to the change of velocity of an object is known as its “inertial mass” and is the mass in Newton’s famous equation F = ma
It also happens that how hard gravity pulls on an object depends on how much stuff there is to pull on. (And conversely, how hard something pulls on something else, that is how much gravity an object “creates” also depends on how much stuff it is pulling with) and thus it’s mass. How hard gravity pulls on an object is known as the “gravitational mass” It may seem logical and intuitive but it’s actually quite difficult to explain why the inertial mass and gravitational mass are exactly the same, it’s an advanced topic. But they are exactly the same. This is part of the reason there is such a great deal of confusion about mass, it’s playing two different parts!
The other reason is that if you want to measure the mass of an object it is very simple to do. You could measure exactly how hard you’re pushing something and how fast it then moves, but this is quite complicated. We also know that gravity pulls more massive things harder. If I put two rocks on a table the heavier rock will push on the table below it with more force because gravity pulls on it harder. And it is very easy to measure forces! And thus if I know that force I can do a little calculation and know the mass of the rock. This practice has become so common that the measurement devices (scales) don’t even tell us the force they measure, they immediately convert it to kilograms. They tell us how many kilograms would produce that force they measure. That force is thus not exactly the same as the mass, that is the weight.
Importantly, weight is the force measured that is produced by an objects mass in gravity. This weight is thus different in places with a different strength of gravity. On Jupiter your mass would be the same as on earth, you are still made from the same stuff, but gravity would pull on you more strongly, thus you would weigh more.
So weight and mass are different things, but for most things it’s the same. A weight of 1 kg is the force exerted on a surface by a mass of 1 kg under Earth’s gravity
Your intuition was right in that grams is mas, not weight.
The best way I’ve had it described is mass is a measure of how hard it is to get something to move. You have to push a 2kg thing twice as hard (over the same time) as a 1kg thing to get them to move the same speed.
Weight is a measure of how much things are attracted to each other through gravity and is a Force; not a mass. Since basically everything is miniscule compared to the earth we don’t really care how much each car is attracted to each other, but how much it is attracted to the earth is very measurable due to the earth’s immense pull.
Since we all live with the same gravity many use weight and mass interchangeably, but 1kg on earth is 1kg in space and 1kg on the moon. 1lb on earth is 0 in space, and like 0.1lb on the moon.
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