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?

Question

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

Answer 1

Weight is gravity acting on mass. Mass is (very roughly) how much substance the object has whether or not it happens to be subject to any significant gravity at the time.

Because the vast majority of us only ever worry about earth gravity and don’t experience any other circumstance people generally use mass and weight interchangeably, but they aren’t exactly the same.

For example: lifting someone on the moon would be easier. That’s because they weigh less on the moon because the moon has less gravity. If they tackle you on the moon, though, they’re still going to hit just as hard because they have the same mass which carries the same kinetic energy at a given speed. None of their substance vanished by the change in gravity, there is just less gravity to act on it.