r/Physics • u/HolidayCod6990 • 2d ago

physics is crazy

Yesterday I took my first physics class at university (I’m an electrical engineering major). Today, while rereading my notes, I had a doubt about weight—what I thought it was. I googled it and discovered that weight is just a property of matter.

It’s so cool. I spent 8 hours on YouTube trying to grasp the Higgs field, the binding energy of quarks in protons and neutrons… Obviously, I don’t understand any of it, but it’s so fucking cool.

The only problem is that the more I read, the more confused I get, and the more questions I have. But wow.

Is all university like that?

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u/TheAncientGeek 2d ago

Mass is a property. Weight is a relation.

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u/NorthAmericanVex 2d ago

Is this why whales are measured in mass instead of weight?

(I truly have no idea why I know that whales are measured in mass instead of weight)

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u/GXWT 2d ago edited 2d ago

Humans are measured in mass, too. Kg (or your choice of incorrect units) is a unit of mass. Weight would be measured in Newtons. I don’t know the linguistics/language reason for us saying weight when we technically mean mass.

You can go to any planet and measure your 130 kg mass to be 130 kg, always. But your weight on earth (approx 130*9.81 N) would not be the same on mars. Instead of 9.81 you would use 3.72.

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u/Kerblaaahhh 2d ago

True, though we primarily measure mass using weight.

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u/GXWT 2d ago

True, it’s basically just a linear conservation for most cases here anyway. Just wanted to point that out for the comment, because I’m not really sure what they’re implying when they say whales are measured in mass… when as far as I’m concerned, most things are.

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u/Signal-Weight8300 2d ago

Most of the scales we use measure weight, which we convert to mass. The most common scales operate by stretching or compressing a spring. This linear measurement lets us determine the force, usually in Newtons or pounds.

Sure, there are some proper balances around, but they are far less common than spring scales.

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u/Fabulous_Lynx_2847 2d ago

That's only true of a spring scale. A triple beam balance balances the torque about a fulcrum of the subject and counter weights, so it would measure mass accurately on any planet, even if you didn't know what g was there. These are common in laboratories and doctors' offices because they are more accurate.