Metric prefixes and unit conversions
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Metric prefixes
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Yotta = 1024 Symbol: Y
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Zetta = 1021 Symbol: Z
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Exa = 1018 Symbol: E
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Peta = 1015 Symbol: P
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Tera = 1012 Symbol: T
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Giga = 109
Symbol: G
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Mega = 106 Symbol: M
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Kilo = 103 Symbol: k
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Hecto = 102 Symbol: h
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Deca = 101 Symbol: da
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Deci = 10-1 Symbol: d
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Centi = 10-2 Symbol: c
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Milli = 10-3 Symbol: m
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Micro = 10-6 Symbol: �
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Nano = 10-9 Symbol: n
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Pico = 10-12 Symbol: p
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Femto = 10-15 Symbol: f
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Atto = 10-18 Symbol: a
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Zepto = 10-21 Symbol: z
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Yocto = 10-24 Symbol: y
Conversion equivalencies for volume
1 US gallon (gal) = 231.0 cubic inches (in3)
= 4 quarts (qt) = 8 pints (pt) = 128 fluid ounces (fl.
oz.) = 3.7854 liters (l)
1 Imperial gallon (gal) = 160 fluid ounces
(fl. oz.) = 4.546 liters (l)
Conversion equivalencies for distance
1 inch (in) = 2.540000 centimeter (cm)
Conversion equivalencies for velocity
1 mile per hour (mi/h) = 88 feet per
minute (ft/m) = 1.46667 feet per second (ft/s) = 1.60934
kilometer per hour (km/h) = 0.44704 meter per second (m/s)
= 0.868976 knot (knot -- international)
Conversion equivalencies for weight
1 pound (lb) = 16 ounces (oz) = 0.45359
kilogram (kg)
Conversion equivalencies for force
1 pound-force (lbf) = 4.44822 newton (N)
Acceleration of gravity (free fall),
Earth standard
9.806650 meters per second per second (m/s2)
= 32.1740 feet per second per second (ft/s2)
Conversion equivalencies for area
1 acre = 43560 square feet (ft2)
= 4840 square yards (yd2) = 4046.86 square
meters (m2)
Conversion equivalencies for pressure
1 pound per square inch (psi) = 2.03603
inches of mercury (in. Hg) = 27.6807 inches of water (in.
W.C.) = 6894.757 pascals (Pa) = 0.0680460 atmospheres (Atm)
= 0.0689476 bar (bar)
Conversion equivalencies for energy or
work
1 british thermal unit (BTU --
"International Table") = 251.996 calories (cal --
"International Table") = 1055.06 joules (J) = 1055.06
watt-seconds (W-s) = 0.293071 watt-hour (W-hr) = 1.05506 x
1010 ergs (erg) = 778.169 foot-pound-force (ft-lbf)
Conversion equivalencies for power
1 horsepower (hp -- 550 ft-lbf/s) = 745.7
watts (W) = 2544.43 british thermal units per hour
(BTU/hr) = 0.0760181 boiler horsepower (hp -- boiler)
Converting between units is easy if you have
a set of equivalencies to work with. Suppose we wanted to
convert an energy quantity of 2500 calories into watt-hours.
What we would need to do is find a set of equivalent figures
for those units. In our reference here, we see that 251.996
calories is physically equal to 0.293071 watt hour. To
convert from calories into watt-hours, we must form a "unity
fraction" with these physically equal figures (a fraction
composed of different figures and different units, the
numerator and denominator being physically equal to
one another), placing the desired unit in the numerator and
the initial unit in the denominator, and then multiply our
initial value of calories by that fraction.
Since both terms of the "unity fraction" are
physically equal to one another, the fraction as a whole has
a physical value of 1, and so does not change the
true value of any figure when multiplied by it. When units
are canceled, however, there will be a change in units. For
example, 2500 calories multiplied by the unity fraction of
(0.293071 w-hr / 251.996 cal) = 2.9075 watt-hours.
The "unity fraction" approach to unit
conversion may be extended beyond single steps. Suppose we
wanted to convert a fluid flow measurement of 175 gallons
per hour into liters per day. We have two units to convert
here: gallons into liters, and hours into days. Remember
that the word "per" in mathematics means "divided by," so
our initial figure of 175 gallons per hour means 175
gallons divided by hours. Expressing our original figure as
such a fraction, we multiply it by the necessary unity
fractions to convert gallons to liters (3.7854 liters = 1
gallon), and hours to days (1 day = 24 hours). The units
must be arranged in the unity fraction in such a way that
undesired units cancel each other out above and below
fraction bars. For this problem it means using a
gallons-to-liters unity fraction of (3.7854 liters / 1
gallon) and a hours-to-days unity fraction of (24 hours / 1
day):
Our final (converted) answer is 15898.68
liters per day. |