Mass or Weight? 1

[mousepotato]

Hi NXers,

Have you ever noticed that Assembly navigator tree (ANT) uses Weight with the units kg?

In my understanding Mass is a fundamental quantity of a body (in kg, grams, etc.) and weight is a force on that body ( by mother earth literally) with units as Newton - N or kgf.
Mass would remain the same in this universe, but weight would differ here on Earth / Moon / Mars etc.

Yeah, we mean MASS when we say WEIGHT in our day-to-day life like "that guy WEIGHS 100 kg", but inside a serious engineering software like Nx, this is not right.
Please correct me if I am wrong or if I am missing something?

Nx 8.0 on TC10

Thx,
mousepotato

 

[JohnRBaker]

In the case of the Assembly Navigator, we're doing exactly what you're doing when you say "that guy WEIGHS 100 kg". The term 'Weight' is being used as a colloquialism. But again, just like when you're talking about your somewhat overweight friend, it's being used with the understanding that it's relative to the where that part is currently at, in this case on a Drawing being read by the people who are manufacturing it, and until we start to colonize other planets, that's going to be right here on Earth, where we can assume that 'kg' is a valid unit of weight.

However, that being said, you are right with respect to one thing and that is that NX is truly a piece of "serious engineering software". Therefore, where it counts like when performing actual calculations and defining formulas for how something will behave, such as when creating engineering formulas using expressions, we do provide for BOTH the concept of Weight and Mass as having different units as well as different values and we enforce this when using expressions in situation where it matters, such as it being invalid to use a Mass in an equation where Force is expected and vice versa. You can see this in the images below:

Mass Units in Expressions.

Force Units in Expressions.

So you're right, there is a difference between Mass and Weight, and when it truly counts, NX provides you complete control over what it is that you're trying to represent and how it's to be used.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.