Ruler

Source: Wikipedia, the free encyclopedia.
This article is about the measuring device-the ruler. For other uses, see Ruler (disambiguation).
"Carpenter's rule" redirects here. For the mathematical unfolding problem, see Carpenter's rule problem.
A variety of rulers
A carpenter's rule
Retractable flexible rule or tape measure
A closeup of a steel ruler
A ruler in combination with a letter scale

A ruler, sometimes called a rule, scale or a line gauge or metre/meter stick, is an instrument used to make length measurements, whereby a length is read from a series of markings called "rules" along an edge of the device.[1] Usually, the instrument is rigid and the edge itself is a straightedge ("ruled straightedge"), which additionally allows one to draw straighter lines.

Variants

Rulers have long been made from different materials and in multiple sizes. Historically, they were mainly

rangefinders
.

Use in geometry

Main article:
Compass and straightedge

In geometry, straight lines between points may be drawn using a straightedge (ruler without any markings on it). Furthermore, it is also used to draw accurate graphs and tables.

A

ruler and compass construction is a construction that uses a ruler and a compass. It is possible to bisect an angle into two equal parts with a ruler and compass. It can be proven, though, that it is impossible to divide an angle into three equal parts using only a compass and straightedge — the problem of angle trisection
. However, if two marks be allowed on the ruler, the problem becomes solvable.

History

The Nippur cubit-rod, c. 2650 BC, in the Archeological Museum of Istanbul, Turkey
A wooden carpenter's rule and other tools found on board the 16th-century carrack Mary Rose

In the history of measurement many distance units have been used which were based on human body parts such as the cubit, hand and foot and these units varied in length by era and location.[3] In the late 18th century the metric system came into use and has been adopted to varying degrees in almost all countries in the world.

The oldest preserved measuring rod is a copper-alloy bar that dates from c. 2650 BC and was found by the German Assyriologist Eckhard Unger while excavating at the Sumerian city of Nippur (present-day Iraq).

Rulers made of

Mohenjo-Daro ruler is divided into units corresponding to 33.5 millimetres (1.32 in) and these are marked out in decimal subdivisions with amazing accuracy, to within 0.13 millimetres (0.005 in). Ancient bricks found throughout the region have dimensions that correspond to these units.[5]

Anton Ullrich invented the folding ruler in 1851. Frank Hunt later made the flexible ruler in 1902.[6]

Curved and flexible rulers

The equivalent of a ruler for drawing or reproducing a smooth curve, where it takes the form of a rigid template, is known as a French curve. A flexible device that can be bent to the desired shape is known as a flat spline, or (in its more modern incarnation) a flexible curve. Historically, a flexible lead rule used by masons that could be bent to the curves of a molding was known as a lesbian rule.[7]

Philosophy

language games in the Philosophical Investigations (1953). He pointed out that the standard meter bar
in Paris was the criterion against which all other rulers were determined to be one meter long. However, there was no analytical way to demonstrate that the standard meter bar itself was one meter long. It could only be asserted as one meter as part of a language game.

See also
  • Accuracy and precision – Characterization of measurement error
  • Dividing engine – Device for marking graduations on measuring instruments
  • Golomb ruler – Set of marks along a ruler such that no two pairs of marks are the same distance apart
  • Measuring instrument
     – Measuring instruments which monitor and control a process
  • Measuring rod – Tool used to physically measure lengths
  • Rolling ruler
  • Scales:
    • Architect's scale
       – Tool used for measuring at a fixed ratio
    • Metric scale
       – Tool used for measuring at a fixed ratio and
    • Engineer's scale
       – Tool used for measuring at a fixed ratio
  • Significant figures – Any digit of a number within its measurement resolution, as opposed to spurious digits
  • Technical drawing tool – Tools and instruments used for accurate and precise manual drafting

References

  1. ^ "ruler noun - Definition, pictures, pronunciation and usage notes - Oxford Advanced Learner's Dictionary at OxfordLearnersDictionaries.com". www.oxfordlearnersdictionaries.com. Archived from the original on 25 October 2017. Retrieved 25 April 2018.
  2. ^ "Steel Rule Has Pocket Clip For Use As A Depth Gauge", Popular Science, December 1935, p. 887 bottom right.
  3. ^ Klein, Herbert A. The science of measurement: a historical survey. Reprint, unabridged, corr. republ. der Ausg. New York, Simon & Schuster, 1974. ed. New York, NY: Dover, 1988. Print.
  4. ^ a b Whitelaw, p. 14.
  5. ^ Whitelaw, p. 15.
  6. ^ "Flexible Ruler Invented by Frank G. Hunt". National Museum of National History. Archived from the original on 30 June 2016. Retrieved 7 June 2016.
  7. ^ "lesbian rule". Oxford English Dictionary (Online ed.). Oxford University Press. (Subscription or participating institution membership required.) (subscription required)

Bibliography

Look up ruler in Wiktionary, the free dictionary.
Wikimedia Commons has media related to Length measuring devices.
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