Half a croissant, on a plate, with a sign in front of it saying '50c'
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Radian Tape

Handy to have a round.
  [vote for,

A flexible measuring tape (think the kind tailors use) marked off, not in inches or centimeters, but in inches or centimeters times pi. The back side has inches or centimeters divided by pi.

Allows one to quicky and easily determine the radius and diameter of a circular object by measuring around the edges, or, using the back side, the circumference by measuring across. No calculations necessary.

(Granted, the occasions on which you would need to do this are likely to be rare.)

gisho, Jun 01 2010

Not exactly what you said, but I have used vernier pi tapes before to determine diameter http://www.pitape.com/
(annoying web site warning) [normzone, Jun 01 2010]

Half of what you want :) http://en.wikipedia.../wiki/Diameter_tape
Is half of a half-baked idea, quarter baked? [goldbb, Jun 01 2010]


MaxwellBuchanan, Jun 01 2010

       Yes, baked per link. I even used one of these to measure the diameter of tires when I teched Indy Cars.
MisterQED, Jun 01 2010

       Also useful would be a relativity-corrected tape measure for measuring things which are travelling at near-light speeds.
hippo, Jun 01 2010

       I want to use some right now to...(It sounds spectacular[+].)
blissmiss, Jun 01 2010

       //elativity-corrected tape measure for measuring things which are travelling at near-light speeds.//   

       An aside: given that things change size when they approach light-speed, and given the principle of microreversibility in physics, it should be possible to make a rubber spaceship, and propel it to light-speed by simply squashing it (or do I mean stretching?).
MaxwellBuchanan, Jun 01 2010

       Yes, you do.
8th of 7, Jun 01 2010

       [normzone], thanks for the link - I was imagining something a lot less precision and calibrated, just a thingy one could pitch in one's toolbox next to the ikea hammer and the screwdriver with sixteen bits, five of which have even been used, but those are very cool.
gisho, Jun 01 2010

       [+] Do the two sets of numbers need to be on opposite *surfaces* of the tape? Surely using the two edges of one face would suffice, and would cut down on printing costs. This is commonly done for tape measures and rulers which show both metric and inches, so I don't see why it wouldn't work for conversions between circumference and diameter.
goldbb, Jun 01 2010

       One measly [+] just isn't enough for this idea, but it's all I can give.
mouseposture, Jun 01 2010


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