scaling

[smeag]

Hi can someone please explain how to derive the formula for general scaling (no.46)?
Ex. A model house has 18.5 in^2 of floor space and weights 4 lb. If scaling principles apply, how much does his 4800 ft^2 house weigh?
Thanks!

[darksaber21]

There really is no formula. The realization is that you need to match powers when setting up proportions. So:

Since weight is a third-power quantity and area is a squared quantity:
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Units must be consistent as well.

[smeag]

Ok , can someone please tell me what I am doing wrong here? Ex. A metal stamping company makes different sized Texas lone stars for yard art from a single spool of metal sheets. If the 2ft tall star weighs
4.4 lbs, how tall is the star that weighs 25 lbs?

This is what I did... (since weight is 3-d, I cubed it, and since length is just 1-d, I left it alone)
(4.4)^3/2 = (25)^3 / x

[darksaber21]

The thing about this is that the thickness is constant (since each star is made from the same sheet, thus implying constant thickness), so only two dimensions of the volume/weight will change. Thus, we need to square the length as oppose to cubing it. Plus, you were cubing/squaring the wrong quantities; it is the other way around.

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[101dalmatians]

For more info., have a look at: viewtopic.php?f=3&t=3232

[101dalmatians]

Readers of the forum:
Sometimes, these scaling problems are so tough that it seems like one of those #36 or 37 or 38 questions that take forever to solve - and finally get them wrong which is another story!
How do you do the ones with like 3 different variables - but only comparing two and it seems like you are comparing volume but not - you know - the confusing problems!
IT comes up on those TMSCA states a lot...

[darksaber21]

I'm sorry, but I can't understand what you are trying to ask. Can you please give an example of what you are talking about? Maybe we can start there with answering your question.

[smeag]

Hi!
Can someone plz help me on the following 2010 state questions?
27, 28, 46, 47, 57... thx!!

[101dalmatians]

I thought that the 2010 state test wsa missing! Where did you find it?