Math help

B

Brian

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If you took an eight foot piece of pipe and bent it into a circle what would the diameter be we have lots of smart people here also what is the formula
 
circumference of a circle is 2 x pi x r or pi x D
r = radius
D = 2r = diameter

so, take 8ft and divide by pi to get diameter
 
those formulae are correct but the thickness of the pipe is going to give you an inner and outer diameter. might be a factor or not depending on what you're working on.
 
I would think the circumference would be eight because that what we started with but my question is what the diameter after bent into the circle
 
2.546 ft, or 30.568 inches (but that's for a line, so not counting the diameter of the pipe itself, which would make the interior diameter smaller and the outside diameter larger).

V/R
 
did this not do it for you:
take 8ft and divide by pi to get diameter = 2.548 ft diameter

onthecreek is right - there will be an inner diameter from the inside to the inside, and an outside diameter form the outside to the outside.. Formula would give you diameter based on middle of the pipe
 
My slide rule only gave me three significant digits: 30.6 inches... :(
 
Wow, Bill, you and I and how many others know what a sliderule is, never mind how to use one! From 1958 to 1962, I was an electrical engineering student at Brooklyn Technical High School, in Brookyn, NY. The sliderule was my friend. Pocket calculators hadn't been invented. Back in the 1980s, I was helping a student I was tutoring do a research paper on "The Sliderule, an Obsolete Invention." Boy, did I feel old! I did, however, still remember how to use one, including the Loga,Loga scales. PS. Due to problems with calculus in college (remember, no calculators), I switched majors from engineering to English and eventually became an English teacher and then a Reading/Study Skills Specialist. Fate has a way of making us what we really should be. After retiring (and becoming bored), I became an Assistant Adjunct Professor of Reading at Suffolk County Community College and I can still do most math in my head, without a calculator! Hy
 
Slide rule:

Water resistant ( Coffee resistant too, thank goodness! )
Needs no batteries
Accurate enough to calculate ( in real time ) the start up of controlled nuclear fission ( research Chicago squash court and the graphite reactor ).
Does not require cellphone or WiFi connection

I actually often miss mine... ( any one of the would do, but I really miss the nice large bamboo and faux ivory Dietzgen )

I had a physics prof who banned digital calculators, and promised an "F" to anyone who gave an answer of greater than 3 digits precision, except if the first digit was "1", in which case, 4 digits.
 
I had a circular slide rule as a freshman in college. Worked well.
Bought an HP 35 my sophomore year (could not afford an HP45). Cost more than most laptops today
 
Brings back wonderful memories. I had a K&E, made of bamboo with a plastic laminate over it for the scales and it even had teflon slides to allow the center section to slide smoothly. Boy, was I a nerd! I loved that slide rule. After college I bought an HP55, in Macy's, no less. Kept that calculator until about 10 years ago. It was fantastic. For those that remember HP calculators, it had RPN (reverse Polish notation) that used a 4 position "stack". It was great!

Young people today use technology but most have no idea of how or why it works. I think they drive and boat the same way. Very sad.
 
Even into the 90s and early 2000s, the Army Field Artillery used slide rules as backup to their digital processors. After all, you still need to be able to put steel on target even when the power goes out. I've been away from the guns for a while and so don't know if Ft. Still still teaches manual gunnery (using slide rules, logarithms, etc.), but I sure hope they do.

V/R
 
quote:
Originally posted by Brian

I would think the circumference would be eight because that what we started with but my question is what the diameter after bent into the circle

Click to expand...


The inner circumference would be 8'. But the outer circumference is unknown because you did not specify the diameter of the pipe.

When the pipe is bent the inside will touch, but there will be a gap in the outside.

G
 
Hummmm the pipe is 8' on all sides and the middle.

After you bend it into a circle the outside would have to be longer than 8' if the inside were still 8' and the pipe touches at all points so unless the pipe stretches or the inside compresses it must become flat. Inner diameter is
D=8'/pi
 
quote:
Originally posted by Brian

If you took an eight foot piece of pipe and bent it into a circle what would the diameter be we have lots of smart people here also what is the formula

Click to expand...


Go get an 8 foot piece of pipe, bend it in a circle, meaure the inner and outer diamter and report back your findings.

We will then give you the answer.
 
If you bend it into a true circle, both flat ends would touch each other completely. Ignoring any stretching caused by the bending itself and any heat which might be applied to enable the pipe to bend without flattening or kinking, the circumference of the circle will be 8' plus the diameter of the pipe. The reason for that is that the original length is actually for a measurement along what would become the center of the pipe when its bent into a circle. Your would then add 1/2 the diameter of the pipe to each side of the circle, measured from the center of the pipe, or, simply, add the diameter of the pipe to the 8'. Assuming 1" diameter pipe, the circumference becomes 96" + 1" = 97". 97" divided by 3.14 (pi) = 30.892". That's the diameter of the outer edge of the circle. The centerline measurement would be 29.892" and the inner diameter would be 28.892". Either way, too tight for a hoola hoop!. Hy
 
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