Igor's Blog
Programming, DIY, Games, Hacks, and Tech

I remember back in school thinking "when will I ever need to use this in real life" during math classes. Today was that day! I had to get the diameter of a copper water cooling pipe that's in my air conditioning utility cupboard and is quite hard to reach.

I do have callipers just for this purpose but when I tried to use them, I couldn't tell if they got all the way around the pipe or not. So I thought that I may as well use the formula for the circumference of a circle to confirm my measurement.
IMG_0317.jpg


I used a flexible tape measure used for sewing to measure around the pipe, which gave me the circumference. In my case it was 243mm.

IMG_0320.jpg IMG_0321.jpg


Now the formula for the circumference is 2 × pi × r. With that and a little bit of algebra it's easy enough to work out the radius...
 Math
First write the formula and the measurements, which are equal one another
243 = 2 × pi × r
Substitute the value for pi, 4 decimal places is close enough
243 = 2 × 3.1415 × r
Multiply pi by 2
243 = 6.283 × r
Change sides for r and adjust to divide
r = 243 ÷ 6.283
Final result for radius
r = 38.675


Now that of course gives the radius and I was after the diameter, so just multiply by two (or I could have just not multiplied pi by 2 above).


 Math
Diameter is 2x the radius
d = r × 2
Substitute the value for radius
d = 38.675 × 2
Final result for diameter
d = 77.35


So the diameter of my pipe according to the calculation is 77.35mm. This is not a standard copper pipe size, which means my circumference measurement was wrong (confirmed later it was off by 5mm). It's important to get this measurement right, however it's not a show stopper if you just need an approximate value and can just match to the closest standard size (you're not likely to have non-standard sized pipes).

Incidentally this is what my callipers said...76mm, which was spot on after all.

IMG_0318.jpg IMG_0319.jpg


-i

comments powered by Disqus
Other posts you may like...

Recent Blog Posts

A hack to create an uber jar with the Maven Shade Plugin using local jar files

Is it worth it? Apple USB-C Digital Multi AV adapter vs a cheap eBay clone

Running X11 graphical applications after changing to another user using 'sudo su'

How to stop Facebook using ad images as post sharing thumbnails

Picking lists for Atari Lynx capacitor replacement kits

Performance - 2012 Retina MacBook Pro vs 2017 MacBook Pro

Look and feel - 2012 Retina MacBook Pro vs 2017 MacBook Pro

Using math to work out the diameter of hard to reach water cooling pipes

How to get the unreachable shard in the Hinterlands in DragonAge Inquisition

Measy RC12 wireless 2.4Ghz keyboard touchpad review

Recent Galleries

Monument Valley 2 is released and does not disappoint

Space Food - Chocolate Ice Cream with Chocolate Chips

Legeod Star Wars AT-DP kit

DIY spare parts computer build with a RAIDMAX Anura case

Fake 'Lepin' brand Lego packaging

Hardwood garden bench with clear resin void filler

Fixing a 3D printer extruder that stopped heating up

Easily increase disk space in a Lenovo Ideapad 100S 14" laptop with an M.2 SSD

Making a multi-piece 3D printed solder spool holder stand

DIY indoor apartment grow light wiring

My Other Web Sites

Igor and Elise's Travels
Riverside Expressway Cam
300 George St Blogumentary

My Online Tools

UUID to OID Converter
Guru JSON-RPC Tester
Extrudifier Object Designer
Travel ┬ÁBlog

Blogs and Friends

Matt Moores Blog
Georgi's FlatPress Guide
Perplexing Permutations
The Security Sleuth
Ilia Rogatchevski
Travelling Fairy

Blog Activity

Blog Activity
Don't forget to
me for more great articles!
Don't show this again