Physical Constants and Conversion Factors

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Physical Constants
Metric Prefixes

Physical Constants:

    c        Speed of light = 3.00 x 10⁸ m/s
    R       Universal gas constant = 8.31 joule/K·mol
    G       Gravitation constant = 6.67 x 10^-11 N·m²/kg²
    k        Boltzmann's constant = 1.38 x 10^-23 joule/K

Metric Prefixes:

    T = tera = trillion = 10¹² = 1,000,000,000,000
    G = giga = billion = 10⁹ = 1,000,000,000
    M = mega = million = 10⁶ = 1,000,000
    k = kilo = thousand = 10³ = 1000
    h = hecto = hundred = 10² = 100
    da = deka = ten = 10¹
    d = deci = one tenth = 10^-1 = 1/10
    c = centi = one hundredth = 10^-2 = 1/100
    m = milli = one thousandth = 10^-3 = 1/1000
    m = micro = one millionth = 10^-6 = 1/1,000,000
    n = nano = one billionth = 10^-9 = 1/1,000,000,000
    p = pico = one trillionth = 10^-12 = 1/1,000,000,000,000

Length:

    1 kilometer = 1000 meters
    1 meter = 100 centimeters
    1 mile = 1 statute mile = 1609.344 meters
    1 mile = 1 statute mile = 5280 feet = 1760 yards = 320 rods = 8 furlongs
    1 inch = 2.54 centimeters
    1 foot = 12 inches = 30.48 centimeters
    1 yard = 3 feet
    1 league = 3 nautical miles
    1 nautical mile = 1852 meters = 1.1508 statute miles = 6076.10 feet
    1 fathom = 6 feet
    1 nautical mile = 1000 fathoms (approximately)
    1 angstrom = 0.1 nanometers = 10^-10 meters
    1 micron = 1 micrometer
    1 light year = 9.46 x 10¹² kilometers
    1 parsec = 3.084 x 10¹³ kilometers = 3.26 light years

Volume:

    1 cubic meter = 1000 liters
    1 liter = 1000 cubic centimeters
    1 liter = the volume of 1 kg of water at its maximum density
    1 liter = 61.02 cubic inches = 1.0567 U.S. fluid quarts
    1 U.S. fluid gallon = 4 U.S. fluid quarts
    1 U.S. fluid quart = 2 U.S. fluid pints
    1 U.S. fluid pint = 2 U.S. fluid cups
    1 U.S. fluid cup = 8 U.S. fluid ounces
    1 British imperial gallon = the volume of 10 pounds of water at 62 degrees F
    1 British imperial gallon = 277.42 cubic inches = 1.201 U.S. fluid gallons
    1 U.S. fluid gallon = 231 cubic inches
    1 register ton = 100 cubic feet

Mass:

    1 kilogram = 1000 grams
    1 slug = 14.59 kilograms
    1 tonne = 1 metric ton = 1000 kilograms

1 kilogram has a weight of 2.20462 avoirdupois pounds at the earth's surface. One often finds the conversion "1 kilogram = 2.2 pounds" (approximately).  It is a useful conversion, but it is worth remembering that the kilogram is a unit of mass while the pound is a unit of force.  The force with which the earth's gravity tugs on a 1-kilogram mass situated at the earth's surface is 2.20462 lbs.

Force:

    1 pound* = 4.448 newtons = 12 avoirdupois ounces  = 32.17 poundals
    1 ton (U.S.) = 1 short ton = 2000 avoirdupois pounds
    1 ton (Britain) = 1 long ton = 2240 avoirdupois pounds
    1 newton = 100,000 dynes

* The "pound" described here is the "avoirdupois pound".  "Avoirdupois weight" is a system of weights used in Britain and in the U.S. for goods other than gems, precious metals, and drugs.  The abbreviations "av.", "avdp.", and "avoir." are sometimes used to denote avoirdupois.  The pound is abbreviated "lb".  For gems and precious metals, one uses "troy weight".  (1 troy ounce = 1.0971 avoirdupois ounce.)  For drugs, one uses "apothecaries' weight."  The advantages of the metric system should be obvious.

Time:

    1 year = 365.25 days (approximately).
        1 tropical year = 365.2422 mean solar days = 365^d 5^h 48^m 46^s
        1 sidereal year = 365.2564 mean solar days = 365^d 6^h 9^m 10^s
    1 day = 24 hours = 1 mean solar day
    1 hour = 60 minutes
    1 minute = 60 seconds

Pressure:

    1 bar = 1,000,000 dynes/cm²
    1 atmosphere = 1.013 bar = 1,013,000 dynes/cm²
    1 atmosphere = 101,300 pascals = 101,300 newtons/m²
    1 atmosphere =  14.70 lb/in² = 14.70 psi = 2116 lb/ft²
    1 atmosphere = 406.8 inches of water = 760 mm of Hg = 76 cm of Hg 

Energy:

    1 joule = 10,000,000 ergs = 10⁷ ergs = 6.242 x 10¹⁸ electronvolts
    1 Btu = 1055 joules
    1 foot-pound = 1.356 joules
    1 kilowatt-hour = 3.6 megajoules
    1 calorie = 4.184 joules
    1 Calorie = "1 food Calorie" = 1000 calories = 1 kcal = 4184 joules
    1 Quad = 1,000,000,000,000,000 Btu = 10¹⁵ Btu = 1.055 x 10¹⁸ joules
    1 electronvolt = 1.602 x 10^-19 joules

Power:

    1 watt = 1 joule/sec
    1 kilowatt = 1000 watts
    1 horsepower = 745.7 watts

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