1.2 UNIT CONVERSION

We sometimes encounter data given in units other than those used in the SI system.
In this case we must convert the units to the SI system using known conversion factors.


1 mile = 1610 ml and 1 hour = 60 min = 3600 s

Wherever “mile” appears, write 1610 m, and where “hour” appears, write
3600 s.
Thus, 30 mi/h = 30 1610 m = 13.4 m/s
3600 s



Length
1 inch (in) = 2.54 cm
1 foot (ft) = 0.3048 m
1 mile (mi) = 5280 ft = 1.609 km
1 m = 3.281 ft
1 km = 0.6214 mi
1 angstrom (A) = 10-10 m
1 light year = 9.461 ´ 1015 m
1 astronomical unit (AU) = 1.496 ´ 1011 m
1 parsec (pc) = 3.09 ´ 1016 m

Mass
1 slug = 14.59 kg
1 kg = 1000 g = 6.852 ´ 10-2 slug
1 atomic mass unit (amu) = 1.6605 ´ 10-27 kg
(1 kg has a weight of 2.205 lb where the acceleration due to gravity is 32.174 ft/s2)

Time
1 day = 24 h = 1.44 ´ 103 min = 8.64 ´ 104 s
1 year = (yr) = 365.24 days = 3.156 ´ 107 s
1 h = 60 min = 3600s

Speed
1 mi/h = 1.609 km/h = 1.467 ft/s = 0.4470 m/s
1 km/h = 0.6214 mi/h = 0.2778 m/s = 0.9113 ft/s

Volume
1 liter (L) = 10-3 m3 = 1000 cm3 = 0.3531 ft3
1 ft3 = 0.02832 m3 = 7.481 U.S gallons (gal)
1 U.S gal = 3.785 ´ 10-3 m3 = 0.1337 ft3


Force
1 pound (lb) = 4.448 newtons (N)
1 N = 105 dynes (dyn) = 0.2248 lb

Work and Energy
1 joule (J) = 0.7376 ft · lb = 107 ergs
1 kilogram-calorie (kcal) = 4186 J
1 Btu (60°F) = 1055 J
1 kilowatt-hour (kWh) = 3.600 ´ 106 J
1 electron volt (eV) = 1.602 ´ 10-19 J

Angle
1 radian (rad) = 57.30°
1° = 0.01745 rad

Pressure
1 pascal (Pa) = 1 N/m2 = 1.450 ´ 10-4 lb/in2
1 lb/in2 = 6.895 ´ 103 Pa
1 atmosphere (atm) = 1.013 ´ 105 Pa = 1.013 bar = 14.70 lb/in2 = 760 torr

Power
1 horsepower (hp) = 550 ft · lb/s = 745.7 W
1 watt (W) = 0.7376 ft · lb/s