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Q & A: What’s the difference between mass and weight?

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Most recent answer: 10/04/2015
Q:
what is the difference between mass and weight
- mohammed (age 11)
san jose,ca,usa
A:
Mohammed -

Awesome question! The difference between mass and weight is that mass is something that everything has no matter where it is. So something's mass will be the same if it's on the Earth, in space, on the moon, or anywhere! Weight, on the other hand, depends on gravity. Unlike mass, your weight is different on the Earth than it would be on the moon. This is because there's more gravity on the Earth than there is on the moon. In space, you'd have no weight at all. Of course, the two are connected. Something with a bigger mass will have a bigger weight than something with a smaller mass if they were both in the same place.
So weight actually depends on both mass and gravity!

-Tamara

(published on 10/22/2007)

Follow-Up #1: Why weighing scales are graduated in kilograms rather than newtons?

Q:
why weighing scales are graduated in kilograms rather than newton's.Why does the reading on the scales increase when the lift moves upwards
- Penny (age 15)
Australia
A:

Scales are used to measure how much material you have. Say, a chemist is only interested in the quantity, not how much something is pulled by gravity. In everyday usage, they appear to be the same since you live at the same place: on Earth and you can roughly convert by a constant g=9.81 N/kg. But this would depend on your planet as well as where on the planet you live due to the axial rotation, though the latter effect is oftentimes not something you could easily detect. So quantifying the force itself is not universal.

Tunc

That means that on a different planet, a spring scale will give the wrong kg reading. It would give the right Newton reading. A balance-type scale would give the right kg reading on another planet but a wrong Newton reading. Mike W.


(published on 10/04/2015)

Follow-up on this answer.