# Thread: Difference between Measurement and Weight

1. ## Difference between Measurement and Weight

Dear teachers,

My little sister asked me what a gram is.
What came to my mind was
"A gram is a measurement unit of weight".

But I thought that weight was a subset of measurement,
"A gram is a measurement unit".

I am not sure which is the best.

Thank you.
Kitty

2. ## Re: Difference between Measurement and Weight

Mass is a physical quantity with which we quantitatively describe a property of objects, namely their resistance against acceleration. Mass is a scalar quantity, as opposed to a vector quantity, which means it has magnitude but no direction. When physicists introduce a scalar quantity like mass, for example, they seek to develop a conventional system for comparison. If I say heavy, it does not mean much. Heavy for Hulk or heavy for Mickey Mouse? Subjective. Physicists want to be objective. In the SI, kilogram is established as the unit of measurement of mass. What is 1kg?
It was agreed and has been used conventionally ever since that 1kg is equal to the resistance of pure water at

V = 1dm3
T = 277K
. We call this the etalon of mass and we compare unknown masses to this when we measure. Each physical quantity has one etalon. If a body is heavier 2.3 times than the etalon, it means m = 2.3kg.

The relationship between mass and measurement is this:
Kilogram is a unit of measurement for mass.

3. ## Re: Difference between Measurement and Weight

A gram(me) is a unit for measuring weight.
A gram(me) is a unit of measurement of weight.

4. ## Re: Difference between Measurement and Weight

Not to be too picky, but mass, not weight.

5. ## Re: Difference between Measurement and Weight

Let us put things straight.

Originally Posted by Barb_D
Not to be too picky, but mass, not weight.
That is not a matter of being picky. That is a matter of being correct (or not). Yes. People often mix the two quantities for reasons still unknown to me.

A gram is a measurement unit of weight mass.
Weight is force, mass is mass. Weight is the force with which an object presses the surface or pulls the suspension.

If I say the weight of a given object is five kilograms, I lose sight of the nature of the quality of weight. Weight is force, and as such, it is measured in Newton. Mass is absolute (in Newtonian physics), weight is not. Weight depends on the state of motion (a), and the pull of gravity (g).
F(weight) = m(għa)
Mass (m) depends on mass-density (ro) and volume(V):
m = roxV.

(I am a physics teacher)

6. ## Re: Difference between Measurement and Weight

Originally Posted by Barb_D
Not to be too picky, but mass, not weight.
I think you are being too picky in this case. Any scientist would agree with you, but for the normal speaker, 'weight' is the word - in BrE, at least.

On that point, I would say that corum's post might be interesting to a scientist (I assume a scientist would know what an 'etalon' is), but is irrelevant to everyday speech and writing.

7. ## Re: Difference between Measurement and Weight

Originally Posted by corum
(I am a physics teacher)
Quite.

8. ## Re: Difference between Measurement and Weight

Originally Posted by fivejedjon
I think you are being too picky in this case. Any scientist would agree with you, but for the normal speaker, 'weight' is the word - in BrE, at least.

On that point, I would say that corum's post might be interesting to a scientist (I assume a scientist would know what an 'etalon' is), but is irrelevant to everyday speech and writing.
I agree, the vast majority of people would use weight (BrE).

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