Posted by *Curbie* on July 2, 2009, 9:35 pm

I went back after the math behind calculating loads exerted on wind

turbine tower masts and I'm still having trouble converting the

formulas to a spread-sheet so the results match the examples given.

The formula I'm having trouble converting is:

(34,000/1.9)[1 - (1/2)(101.8/132)^2] = 10,994

My question is how do I convert the contents of the left square

bracket "[" and right square bracket "]" to spread-sheet expression?

Or maybe just what is the purpose of the brackets.

Thanks for any help.

Curbie

Posted by *vaughn* on July 2, 2009, 10:08 pm

*> I went back after the math behind calculating loads exerted on wind*

*> turbine tower masts and I'm still having trouble converting the*

*> formulas to a spread-sheet so the results match the examples given.*

*> The formula I'm having trouble converting is:*

*> (34,000/1.9)[1 - (1/2)(101.8/132)^2] = 10,994*

*> My question is how do I convert the contents of the left square*

*> bracket "[" and right square bracket "]" to spread-sheet expression?*

*> Or maybe just what is the purpose of the brackets.*

*> Thanks for any help.*

Just change those square brackets to round ones. They were probably only

made square to help us humans keep track of things. Computers (even cheap

scientific calculators) can handle multiple nested round brackets just fine.

Vaughn

Posted by *Curbie* on July 2, 2009, 11:34 pm

Vaughn,

*>Just change those square brackets to round ones.*

That worked for me in the past but using this spread-sheet expression:

(34000 / 1.9) * (1 - (1 / 2) * (101.8 / 132)^2) = 12,573

where their example is:

(34,000/1.9)[1 - (1/2)(101.8/132)^2] = 10,994

Different results, and since these formulas where taken from some

college physics department, I have to be interpreting that formula

incorrectly.

http://physics.uwstout.edu/StatStr/Statics/Columns/colse62c.htm

I always look for examples with results so I can check my math for

just this sort of mis-interpretation.

Curbie

Posted by *Neon John* on July 3, 2009, 12:39 am

I worked this out by hand on a calculator to make sure I got my

operator precedence correct and got your answer of 12,573. I can't

get 10,994 using any combination of the numbers, even abusing

precedence rules.

I ran the formula using square root instead of square, figuring that

the guy might have hit the wrong key on his calculator. That produces

10,037. Closer but no cigar. I think that he made a math error. Why

not drop him a note and ask?

John

wrote:

*>Vaughn,*

*>>Just change those square brackets to round ones.*

*>That worked for me in the past but using this spread-sheet expression:*

*>(34000 / 1.9) * (1 - (1 / 2) * (101.8 / 132)^2) = 12,573*

*>where their example is:*

*>(34,000/1.9)[1 - (1/2)(101.8/132)^2] = 10,994*

*>Different results, and since these formulas where taken from some*

*>college physics department, I have to be interpreting that formula*

*>incorrectly. *

*>http://physics.uwstout.edu/StatStr/Statics/Columns/colse62c.htm *

*>I always look for examples with results so I can check my math for*

*>just this sort of mis-interpretation.*

*>Curbie*

Posted by *Curbie* on July 3, 2009, 1:16 am

I'm sorry John, I didn't mean for anyone to run the calculations, just

explain the use of the "[ ]".

Do you think those "[ ]" could be replaced with "( )", it seems there

has to be more than that and that one of the students would have run

the math and gleefully pointed out the error (seems that would to be

worth some extra credit)?

*> Why not drop him a note and ask?*

I'll try, I've never had any luck doing that, their pretty busy.

Thanks,

Curbie

> I went back after the math behind calculating loads exerted on wind> turbine tower masts and I'm still having trouble converting the> formulas to a spread-sheet so the results match the examples given.> The formula I'm having trouble converting is:> (34,000/1.9)[1 - (1/2)(101.8/132)^2] = 10,994> My question is how do I convert the contents of the left square> bracket "[" and right square bracket "]" to spread-sheet expression?> Or maybe just what is the purpose of the brackets.> Thanks for any help.