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2003-01-28
There are seven (7) definitions for the ton... and not one
of them would work in the situation. What utter confusion!!!
ton (tn or T or t) [1]
a traditional unit of weight equal to 20 hundredweight. In
the United States, there are 100 pounds in the
hundredweight and exactly 2000 pounds (907.185 kilograms) in the ton. In
Britain, there are 112 pounds in the hundredweight and 2240 pounds (1016.047
kilograms) in the ton. To distinguish between the two units, the British ton is
called the long ton and the American one is the short
ton. In old England, a "tun" was a large cask used to store wine.
Because these tuns were of standard size, more or less, the tun came to
represent both a volume unit, indicating the capacity of a cask, and also a
weight unit, indicating the weight of a cask when it was full. The best symbol
to use for this unit is tn. In the U.S. mining industry, T is used
to distinguish the traditional ton from the metric ton, but T is is the SI symbol for the tesla.
The symbol t, traditionally used for the long or short ton, is now
reserved for thr metric ton.
ton (t) [2]
a metric unit of mass, equal to 1000 kilograms, or approximately 2204.623
pounds avoirdupois. This metric ton is a bit smaller than the
British long ton. The metric ton is now known officially as the
tonne (see below).
ton (RT or rT) [3]
a unit used traditionally to measure the cargo capacity of a merchant ship.
During the Middle Ages, merchant ships were rated by the number of tuns of wine
they could carry. Today the merchant marine ton is defined to be exactly 100
cubic feet, or approximately 2.8316 cubic meters. This unit is often called the
register ton, since it is recorded in official registers of
ships. The symbol RT seems to be in wide use for this unit, but it is
also used for the refrigeration ton (definition [7] below).
ton (DT or dT) [4]
a unit of volume used traditionally to measure the "displacement" of ships,
especially warships. One way to describe the size of a ship is to state the
volume of sea water it displaces when it is afloat: in other words, the volume
of that part of the ship below the waterline. The actual weight of sea water
varies somewhat according to its temperature and how salty it is, but for this
purpose it has been agreed that a long ton of sea water occupies about 35 cubic
feet. Accordingly the displacement ton is defined to be exactly
35 cubic feet, or approximately 0.9911 cubic meter. Since this is a much smaller
unit than the register ton, warships have a much higher "tonnage" than merchant
ships of approximately the same dimensions. The symbol DT is recommended
for this unit.
ton (FT) [5]
a traditional unit of volume used for measuring the cargo of a ship, truck,
train, or other freight carrier. This freight ton is exactly 40
cubic feet, or approximately 1.1326 cubic meters. However, the term "freight
ton" is also being used to mean a metric ton of freight, volume not specified.
Perhaps because of this confusion, the 40 cubic foot unit is often called the
measurement ton (MTON). But the confusion seems impossible to dispel;
some shippers are now using "measurement ton" to mean a metric ton of freight.
(The way out of this dilemma is simple: measure volume in cubic meters and
weight in metric tons.)
ton (tn or T) [6]
a unit of energy used for measuring the energy of an explosion, especially a
nuclear explosion. In this usage, one ton is supposed to be the amount of energy
released by the explosion of one short ton of TNT. This is defined in the U.S.
to equal exactly 4.184 gigajoules (GJ) or
roughly 4 million Btu.
ton (RT) [7]
a unit of power used in refrigeration engineering. One ton of refrigeration
is intended to be the power required to freeze one short ton of water at 0�C in
24 hours. This is assumed to be exactly 12 000 Btu per hour (Btu/h
or "Btuh"), which is equivalent to 200 Btu/min, 3.516 853 kilowatts, 4.7162
horsepower,
or 0.8396 (kilogram) Calorie per
second (Cal/s). The symbol RT seems to be in wide use for this unit, but
it is also used for the register ton (definition [3] above).
John
----- Original Message -----
Sent: Tuesday, 2003-01-28 17:57
Subject: [USMA:24656] Cubic Tons?
Has anyone heard of cubic tons and what does it
mean?
Gabriel Baird of the Capital News Service said on
2003 January 28: ". . . Ford Explorer gets less than 20 mpg and emits 11.6
cubic tons of greenhouse gases per 15,000 miles, according to U.S. Department
of Energy estimates."
This is another example of the screwed up use of
units which the SI cold easily straighten out.
Stan Doore
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