knot is a unit of speed. It is not an System
International (SI) unit. It is
accepted (although discouraged) for use with the SI, since it is used
around the world for maritime and aviation purposes.
knot = 1 nautical mile per hour or 1852 metres per hour precisely.
This is the definition used in most, if not all, modern
knot is equivalent to:
some sailing ships, speed was measured by casting the log
from the stern. The log was relatively immobile, and attached by
line to a reel. Some sources suggest that knots
placed at a distance of 47 feet 3 inches (14.4018 m) passed
through a sailor's fingers, while another used a 28 second
sandglass to time the operation. The knot count would be
reported and used in the sailing master's dead reckoning and navigation.
This method gives a value for the knot of 20.25 in/s, or 1851.66
m/h. The difference from the accepted value today is a bit less
than 0.02%. Because
a knot is already a measure of speed, the expression "knots
per hour" is a solecism. Taken literally (nautical
mile/hour²), it would be a measure of acceleration.
is "knots true airspeed", a measure of an
aircraft's true airspeed through the air
is "knots indicated airspeed", meaning the
airspeed shown on the airspeed indicator
is "knots calibrated airspeed", or indicated
airspeed corrected for position error
is "knots equivalent airspeed", which is
calibrated airspeed corrected for compressibility effects.
would be sailor must know his or her ropes and become familiar
with some common knots, just to be able to tie up a boat to a
jetty. Then there is anchoring, then safety at sea.
There are all kinds of rope and all kinds of knots, each with a
different use. A 'Knot' is also a measure of speed in
water, which gains its name from the distance between two knots
of a piece of rope.