TABLE 2. ? 



FUNDAMENTAL AND DERIVED UNITS- 

 Conversion Factors. 



To change a quantity from one system of units to another: substitute in the corresponding 

 conversion factor from the following table the ratios of the magnitudes of the old units to the 

 new and multiply the old quantity by the resulting number. For example: to reduce velocity 

 in miles per hour to feet per second, the conversion factor is lr l ; I = 5280/1, t= 3600/1, and 

 the factor is 5280/3600 or 1.467. Or \ve may proceed as follows: e. g., to find the equivalent of 

 I c.g.s. unit of angular momentum in the pel. ft. m. unit, from the Table t g cm~/sec.=jc Ib. ft. 2 /rnin, 

 where x is the factor sought. Solving, x=ig/\b. X cm' 2 /ft.' 2 X min./sec. = i X .002205 X .001076 

 X 6o=.oooi42c;. 



The dimensional formulae lack one quality which is needed for completeness, an indication of 

 their vector characteristics; such characteristics distinguish plane and solid angle, torque and 

 energy, illumination and brightness. 



(a) FUNDAMENTAL UNITS. 



The fundamental units and conversion factors in the systems of units most commonly used 

 are: Length [/J; Mass \_m~\\ Time [f\\ Temperature {B~]\ and for the electrostatic system, 

 Dielectric Constant [&]; for the electromagnetic system, Permeability [ju]. The formulae 

 will also be given for the International System of electric and magnetic units based on the units 

 length, resistance [Y], current [f], and time. 



(b) DERIVED UNITS. 



* For these formulae the numbers in the last column are the exponents of F where F refers to the luminous flux. 

 For definitions of these quantities see Table 299, page 259. 



SMITHSONIAN TABLES. 



