Scale vs. mass vs. weight for

[wcfn100]

Halve the gravitation force and you could still calibrate the weighbridge. All the bridge does is determine the ratio between the object and the reference. Don't let the measuring instrument cloud the issue.

Yeah that light bulb finally went off.

Why do you claim that a ton would be 332 pounds on the moon? Your ton is defined as 2000 pounds. Why would it become something different? Let's say your ton is a block of steel. By taking it to the moon the volume hasn't changed nor has the density so why is it no longer 2000 pounds?

I use ton and pound as units of weight (or force of gravity on a mass).  So when I say a ton, I mean something that weighs a ton on earth (since that's were I live).  And IFAIK, if you weigh a certain amount on earth, you'll weigh 1/6th that weight on the moon.   Please correct tme if any of that is in error.

I have never found any reference that says railroads use mass to calculate how much stuff is in a boxcar but it would seem that is what they do.  I don't think that changes anything to do with the intent of this thread however, do it?  - I was going to edit that 'do it', but I'll just leave it there to remember how late it was when I tried to have this discussion.


When you're reading through the previous posts, please keep in mind that this was never intended to become such a physics discussion, I know I'm very rusty, so I'm sure things were written that won't hold up to any scrutiny. ;D



Jason

[wcfn100]

I think my DCC issue if far more important  :-*

Maybe we can spin this off into a third thread.   

re: DCC

Get over it.  Spend the extra $12 and get a 44 tonner.  And then etch me some older hoods.

Jason

[Mark4]

I use ton and pound as units of weight (or force of gravity on a mass).  So when I say a ton, I mean something that weighs a ton on earth (since that's were I live).  And IFAIK, if you weigh a certain amount on earth, you'll weigh 1/6th that weight on the moon.   Please correct tme if any of that is in error.

I have never found any reference that says railroads use mass to calculate how much stuff is in a boxcar but it would seem that is what they do.  I don't think that changes anything to do with the intent of this thread however, do it?  - I was going to edit that 'do it', but I'll just leave it there to remember how late it was when I tried to have this discussion.

Whether you weigh the same on the moon as on earth or 1/6 as much depends on your definition of weight. 

When it comes to human bodies if one intends to lose weight one generally wishes reduce how much body there is. If you can achieve your weight-loss objectives by moving to a lower gravitational field then weight implies force. I suspect, however, that a loss of body mass is what is desired. In that case weight implies mass. Similarly, in trade it is generally (I suspect) the amount of "stuff" that is of interest rather than the force that gravity exerts on it.

[wcfn100]

So maybe you can chime in on what started this all.

The question was regarding the new bachmann 44 ton locomotive and how many cars it might pull as compared to the prototype.

I made the point that a NMRA weighted 40' box car ~.95oz is much heavier than it's prototype counterpart which would effect the pulling comparison.

Jason

[Mark4]

So maybe you can chime in on what started this all.

The question was regarding the new bachmann 44 ton locomotive and how many cars it might pull as compared to the prototype.

I made the point that a NMRA weighted 40' box car ~.95oz is much heavier than it's prototype counterpart which would effect the pulling comparison.

Jason

6

[inkaneer]

Suppose I had a boxcar filled with lead and another indentical boxcar filled with feathers.  Which boxcar weighs more? 


Answer. The cars weigh the same.


Why?


They are indentical.   The loads weigh differently because they are not identical.  So if we take the boxcar without any load and scale it down to 1:160 scale we would need to take the three dimensions of heigth, width and depth and reduce each one 1:160. 

Why?

Objects that weigh anything occupy space [three dimensional]  Single dimensional objects such as a point or a line have no weight.  Two dimensional objects like a square or a triangle have no weight.  Add the third demsion and you have weight.  This is why your module weighs more than your full size plans written on paper.  Your plans are only 2 dimensional, your module three dimensional. So since weight involves three dimensions of height weight and depth and you are scaling each of those by 160 then weight also must be reduced by 160 three times [once for each dimension].   

I am going to rest now as my brain is overheating.

[bicknell]

I always knew Physics teachers had it hard, but I just re-read the thread from the beginning and wow....

http://en.wikipedia.org/wiki/List_of_basic_physics_topics

In particular....

http://en.wikipedia.org/wiki/Mass
http://en.wikipedia.org/wiki/Density
http://en.wikipedia.org/wiki/Force_(physics)
http://en.wikipedia.org/wiki/Law_of_universal_gravitation

That force one is extra important to understand how grades affect your rail road as well...