Ever wanted to know how many gallons would be in a straw around the world?

[UniTyler]

Now is your chance! Here you get to find out how many feet of straw would go around the world and also how many gallons of water would fit inside a straw that was wrapped around the world! This is the product of extreme boredom..... (Copywrite 2005 - Tyler C.)

[UniTyler]

And the moment you've all been waiting for:

[UniTyler]

(Can you believe I didn't even do that on perpose?!? Whew, twice in a row....must be my old age....) Here it REALLY is!

[James_Potter]

heh...wowzers...that made me laugh.

[john_childs]

How did you figure that 20 straws will hold 4 oz?
Did you measure the length and diameter then compute the volume? Or did you fill a straw with water 20 times, dump each straw full of water into a measuring cup and then measure how much water was in the measuring cup?

And what happens if you use straws from McDonald's?

[bugman]

Originally posted by john_childs
How did you figure that 20 straws will hold 4 oz?
Did you measure the length and diameter then compute the volume? Or did you fill a straw with water 20 times, dump each straw full of water into a measuring cup and then measure how much water was in the measuring cup?

And what happens if you use straws from McDonald's?

Come on John, this is one of his more valuable posts. Is his math correct? Assuming his starting figures are good numbers, which for our purposes should be good enough.:D

[UniTyler]

Originally posted by john_childs
How did you figure that 20 straws will hold 4 oz?
Did you measure the length and diameter then compute the volume? Or did you fill a straw with water 20 times, dump each straw full of water into a measuring cup and then measure how much water was in the measuring cup?

I did the water in the straw 20 times in a measuring cup thing.

Originally posted by john_childs
And what happens if you use straws from McDonald's?

Those are way bigger than normal, so it wouldn't be the same.

[Catboy]

Originally posted by UniTyler
Those are way bigger than normal, so it wouldn't be the same.

WRONG. McDonalds straws are barely bigger in any way, however, due to that chaos theory, yes the final result would be much much bigger!!! CHAOS THEORY!!!

[sevenasterisks]

I think its pretty cool (?) the way you start out with 1-2 significant figures, and end up with like 16! I tend to do the same thing, so that if I use it for any other calculations, it will be as accurate as possible :)

[john_childs]

Originally posted by sevenasterisks
I think its pretty cool (?) the way you start out with 1-2 significant figures, and end up with like 16! I tend to do the same thing, so that if I use it for any other calculations, it will be as accurate as possible :)
Yes, failing to keep all the extra digits in the memory of the calculator will cause the final answer to be off by a little bit. Case in point, the final result is actually 318088.01117578064516 gallons of water per Earth diameter sized straw if you carry out the decimals a little bit farther rather than truncating them when you write them down from the calculator display. Can't let those extra digits go to waste. :D

I declare Tyler's answer to be incorrect because he blows it at the 5th place after the decimal point.

[markf]

if you "add" significant figures you'll be less precise. well, put another way: you won't know how far you might be off. granted if you measure something to the milimeter and it comes out to be 1 meter, you don't just have 1 sigfig, you have 4. One for each digit in the 1000 mm in one meter.

[john_childs]

The easier way to do those types of calculations involving lots of unit conversions is to write it out as a series of ratios with the correct units all multiplied together and cancel out all the units till you're left with what you want.

It's much easier to keep the units straight when you do the calculation this way.

For this straw problem you would end up with a calculation like this:

[Loosemoose]

I was always taught (in maths & physics) that you should always discard significant figures (or decimal places) beyond the maximum accuracy of your initial values. So since tylers lowest level of accuray is 2 d.p (the straw length) his final figure should be quoted as 318088.01. I think its to stop you from 'inventing' accuracy, or something.]

lol, gallons per earth_diameter, thats a classic unit.
Did you know the speed of light is 1.8x10^12 Furlongs per Fortnight? I love that unit.

Loose.

[rob.northcott]

It's the circumference of the Earth, not the diameter. Tyler was talking about a straw long enough to go round the Earth, not through it.

[yoopers]

Also, I believe I've heard that the earth has a bigger circumference around the equator than it does north to south. Which way are your straws going to lay? Also, if you lay them north to south, then you've got to figure in expansion of the water when it freezes at the poles.

[yoopers]

Originally posted by UniTyler
(Copywrite 2005 - Tyler C.)
Tyler,

Be sure to copyright your work.

[habbywall]

i still dont understand how you figure out how much water could fit in a straw, did you like make a little stray lid or what?

[UniTyler]

Originally posted by rob.northcott
It's the circumference of the Earth, not the diameter. Tyler was talking about a straw long enough to go round the Earth, not through it.

Yea, JC, I'm a unicyclist not a pogo-sticker!

[Wheel Rider]

Originally posted by UniTyler
Yea, JC, I'm a unicyclist not a pogo-sticker!
Since a person who rides a unicycle is a unicyclist, wouldn't a person who rides a pogo-stick be a pogo-stickist?

[Jim_Rob]

Originally posted by Loosemoose
I was always taught (in maths & physics) that you should always discard significant figures (or decimal places) beyond the maximum accuracy of your initial values. So since tylers lowest level of accuray is 2 d.p (the straw length) his final figure should be quoted as 318088.01. I think its to stop you from 'inventing' accuracy, or something.]

Loose.

Actually, that's not how significant figures work. His measurement of the straw has three significant figures in it, therefore his answer should have at most 3 sig figs too, so it should be 318000

Now, if you quote the uncertainty in a measurement; say the length is 7.75 +/- 0.05, then that can change things again. You would then propagate that error through the calculation as a relative error, 0.05/7.75 and add up the relative errors, RMS (root-mean-square), to get the uncertainty in the final number.

Damn, I shudda been a perfesser.

[john_childs]

Originally posted by rob.northcott
It's the circumference of the Earth, not the diameter. Tyler was talking about a straw long enough to go round the Earth, not through it.
I goofed there. I was meaning circumference but wrote diameter. That's what happens when you try to put something together quickly at 2 am. At least my answer is more accurate than Tyler's. :p

Here's a corrected version

[johnfoss]

Sorry guys, I'm still back at McDonald's, trying to figure out which size straw to use. That was never given in the original question, so I am unable to properly complete my homework assignment.

It sounds like a fun equation though, but you need to finish the question to get an accurate answer. What is the inside diameter of your straw (length doesn't matter)? Also, how are you measuring the circumference of the earth? It's lumpy, you know. If you agree on those two figures it should be pretty easy to figure out an accurate result.

I like the McDonalds straws on a hot day. They're definitely fatter. If you think otherwise, you must only eat at other places with fat straws. Try the straws at the bar sometime! :D

[litldude2]

So would the straws go up and down mountains and stuff or right throught them? Does the circumference of the earth imply its a perfectly smooth sphere?

[johnfoss]

And the bigger question, at what altitude is the straw proposed to be as it rounds the earth? Sea level is probably the basis for circumference figures. Raise it even a foot, and the distance changes quite a bit! Raise it real high, and the water starts changing in volume, I think...

[john_childs]

Originally posted by johnfoss
And the bigger question, at what altitude is the straw proposed to be as it rounds the earth? Sea level is probably the basis for circumference figures. Raise it even a foot, and the distance changes quite a bit! Raise it real high, and the water starts changing in volume, I think...
Wrap a string all the way around the equator. Now lift the string so it is 1 foot above the ground all the way around the equator. The new string is only going to be 2pi longer or about six feet longer than the other string.

[manon1wheel]

Originally posted by john_childs
The easier way to do those types of calculations involving lots of unit conversions is to write it out as a series of ratios with the correct units all multiplied together and cancel out all the units till you're left with what you want.

It's much easier to keep the units straight when you do the calculation this way.

For this straw problem you would end up with a calculation like this:


john joh john john john... its good enough....thats only off by like .999 ounces in all

[BillyTheMountain]

Buckminster Fuller calculated that if humans stood on each others' shoulders, they would make nine chains to the moon.

How many straws would it take to reach the moon?

Billy

[BillyTheMountain]

Originally posted by BillyTheMountain
Buckminster Fuller calculated that if humans stood on each others' shoulders, they would make nine chains to the moon.

How many straws would it take to reach the moon?

Billy

That was the entire Earth's population, back in the 1970s.

[yoopers]

Originally posted by BillyTheMountain
Buckminster Fuller calculated that if humans stood on each others' shoulders, they would make nine chains to the moon.

I don't want to be the one on the bottom.

[john_childs]

Originally posted by manon1wheel
john joh john john john... its good enough....thats only off by like .999 ounces in all
but but but but there's all those extra decimal points of accuracy that you lose if you don't do it right. If the straw was full of beer that extra ounce would be important. You can't be losing beer due to dropped decimals. That would be like buying a pint of beer and only getting 14 ounces of beer. It's just wrong. :eek:

The comments about accuracy are all tongue-in-cheek. The serious part of the post was to show an alternative way of setting up the problem and doing the calculation. The alternative way isn't so much about accuracy as about doing it easier.

[Seager]

This would be WAY easier in metric.

Take diameter of straw and length of straw in cm.
multiply pi x radius of straw squared x circumfrence of world (in cm - (just take kilometers x 100,000))

This = cubic cm of straw around world. I cubic centimeter = 1 ml. Divide by 1000 to get liters. You could do the entire thing in Meters to start if you want, since 1 cubic meter = 10 liters.

Way easier than all those damn conversion factors. This is why science is done in metric. You don't even have to do any of that stupid measuring cup stuff, AND this way you could figure in overlap if you wanted.

[yoopers]

Hmmm...a technology spinoff wrench in the works:

http://www.eblong.com/zarf/review/review-33.html#s1

[habbywall]

how much water would be in straws if your nose was full of them?

[john_childs]

Originally posted by Seager
This would be WAY easier in metric.

It would only be slightly easier in metric. The basic calculations would be exactly the same. The difference would be in the conversion factors. Metric conversions are nice numbers. Imperial conversions are messy. Metric doesn't mean that you don't have to do conversions.

You can convert cubic inches to gallons. You can calculate the volume of a straw and convert that volume to gallons or ounces. The basic calculations are exactly the same as what you'd do for metric. Only the conversion factors will differ.

Calculating significant digits and relative errors (+/- error values) is much easier in metric than imperial units. But we're not doing that. We're just doing the basic calculation.

[fexnix]

Metric and Litres and it would be as easy as a pancake.