FFF system
The Furlong/Firkin/Fortnight (FFF) system is a set of units that uses impractical measurements not seriously deemed suitable for scientific or engineering use. The length unit of the system is the furlong, the mass unit is the mass of a firkin of water, and the time unit is the fortnight.[1] Like the SI or metre-kilogram-second system, there are derived units for velocity etc.
The FFF system is mainly a humorous system of units and is not used in practice, although it has been used as an example in discussions of the relative merits of different systems of units.[1][2] Some of the FFF units, notably the microfortnight, have been used jokingly in computer science. Besides having the meaning "any obscure unit,"[3] furlongs per fortnight have also served frequently in classroom examples of unit conversion and reducing a unit's fraction.[4][5]
Contents |
[edit] Base units and definitions
| Unit | Abbreviation | Dimension | SI unit | Imperial unit |
|---|---|---|---|---|
| furlong | fur | length | 201.168 m | 220 yards |
| firkin | fir | mass | 40.8233133 kg | 90 lb[6] |
| fortnight | ftn | time | 1,209,600 s | 14 days |
[edit] Notable multiples and derived units
[edit] Microfortnight
One microfortnight is equal to 1.2096 seconds.[7] This has become a joke in computer science because in the VMS operating system, the TIMEPROMPTWAIT variable, which holds the time the system will wait for an operator to set the correct date and time at boot if it realizes that the current value is bogus, is set in microfortnights. This is because the computer uses a loop instead of the internal clock which has not been activated yet to run the timer.[8] In a further twist, the documentation notes that "[t]he time unit of micro-fortnights is approximated as seconds in the implementation."[9]
Millifortnights (about 20 minutes) and nanofortnights (1.2096 milliseconds) have also been used occasionally in computer science, usually in an attempt to be deliberately over-complex and obscure.
[edit] Furlong per fortnight
One furlong per fortnight, a speed which would be barely noticeable to the naked eye, converts to:
- 1.663×10−4 metre per second
- roughly one centimetre per minute (to within 1 part in 400).[10]
- 5.987×10−4 km/h
- 6.548×10−3 inch per second
- roughly three eighths of an inch per minute
- 3.720×10−4 mph
- the speed of the tip of an hour hand on a clock, measuring 1.143 metres (3.751 ft) in length
- the speed of the tip of a minute hand on a clock, measuring 9.528 centimetres (3.751 inches) in length
- the speed of the tip of a second hand on a clock, measuring 1.588 mm (1⁄16 of an inch) in length
Thus:
- a car travelling at 60 km/h (37 mph) has a speed of 1.00×105 furlongs per fortnight;
- an airplane cruising at 420 knots or 216.2 m/s (i.e., typical 0.8 Mach cruise) is travelling at 1.300×106 furlongs per fortnight;
- the speed of light in vacuum is approximately 1.803×1012 furlongs per fortnight, or rather 1.803 terafurlongs per fortnight;
- fingernails grow approximately 3 mm per month or 6.96 microfurlongs per fortnight (6.96×10−6 furlongs per fortnight);
- human hair grows between 2 and 4.5 times as fast;
- a garden snail has a top speed of about 78 furlongs per fortnight.
[edit] Firkins per fortnight
Like the more common furlongs per fortnight,[3] firkins per fortnight have been used with the meaning "any obscure unit."[11]
[edit] Notes and references
- ^ a b Stan Kelly-Bootle, "As Big as a Barn?", ACM Queue, March 2007, pp. 62-64.
- ^ John D. Neff, "Imbedding the Metric," The Two-Year College Mathematics Journal, Vol. 14, No. 3 (Jun., 1983), pp. 197-202.
- ^ a b For example, in Jack G. Ganssle, The art of designing embedded systems, 2nd ed., Newnes, 2008, ISBN 0750686448, p. 50.
- ^ Giambattista, Alan; Richardson, Betty McCarthy & Richardson, Robert C. (2004). College Physics. Boston: McGraw Hill. p. 20. ISBN 0070524076.
- ^ Stephan, Elizabeth A.; Park, William J.; Sill, Benjamin L.; Bowman, David R. & Ohland, Matthew W. (2010). Thinking Like an Engineer: An Active Learning Approach. Prentice Hall. p. 259. ISBN 0136064426. http://books.google.com/books?id=SWGO4ZpQly4C&pg=PA259.
- ^ The firkin of the FFF System is defined as the mass of an imperial firkin (9 imp gal) of water. The imperial gallon was originally defined as the volume of 10 lb of distilled water (weighed according to specific conditions). From this definition a density of 10 lb/imp gal is derived, giving the firkin of water a mass of 90 lb.
- ^ Robert Slade, Dictionary of information security, Syngress, 2006, ISBN 1597491152, p. 122.
- ^ "microfortnight". http://catb.org/jargon/html/M/microfortnight.html. Retrieved 2007-07-06.
- ^ "HP OpenVMS System Management Utilities Reference Manual". http://h71000.www7.hp.com/DOC/82FINAL/6048/6048pro_096.html. Retrieved 2008-11-26.
- ^ Indeed, if the inch were defined as 2.5454... cm rather than 2.54 cm exactly, it would be 1 cm/min. "FAQ for newsgroup UK.rec.sheds, version 2&3/7th" (TXT). 2000. http://www.uk-rec-sheds.org.uk/faq60.txt. Retrieved 2006-03-10.
- ^ Page-Jones, Meilir & Constantine, Larry L. (2000). Fundamentals of object-oriented design in UML. Addison-Wesley. p. 235. ISBN 020169946X.
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