Engineering Fundamentals: An Introduction to Engineering, 4th ed.c

6.2 Systems of Units 135

TABLE 6.2 The List of Decimal Multiples and Prefixes Used with SI Base Units

Multiplication Factors Prefix SI Symbol

1,000,000,000,000,000,000,000,000 10

24

yotta Y

1,000,000,000,000,000,000,000 10

21

zetta Z

1,000,000,000,000,000,000 10

18

exa E

1,000,000,000,000,000 10

15

peta P

1,000,000,000,000 10

12

tera T

1,000,000,000 10

9

giga G

1,000,000 10

6

mega M

1000  10

3

kilo k

100  10

2

hecto h

10  10

1

deka da

0.1 10

 1

deci d

0.01 10

 2

centi c

0.001 10

 3

milli m

0.000,001 10

 6

micro m

0.000,000,001 10

 9

nano n

0.000,000,000,001 10

 12

pico p

0.000,000,000,000,001 10

 15

femto f

0.000,000,000,000,000,001 10

 18

atto a

0.000,000,000,000,000,000,001 10

 21

zepto z

0.000,000,000,000,000,000,000,001 10

 24

yocto y

this book. Starting in Chapter 7, we will discuss their physical meaning, their significance and

relevance in engineering, and their use in engineering analysis.

British Gravitational (BG) System

In the British Gravitational (BG) system of units, the unit of length is a foot (ft), which is equal

to 0.3048 meter; the unit of time is a second (s); and the unit of force is a pound (lb), which is

equal to 4.448 newton. Note that in the BG system, a pound force is considered a base or primary

unit and the unit of mass, while theslugis derived from Newton’s second law. When one slug is

subjected to one pound force, it will accelerate at a rate of 1 foot per second squared (ft /s

2

). That

is: 1 lb(1 slug)(1 ft /s

2

). In the British Gravitational system, the unit of temperature is expressed

in degree Fahrenheit (F) or in terms of absolute temperature degree Rankine (R). The relation-

ship between the degree Fahrenheit and degree Rankine is given by:

The relationship between degree Fahrenheit and degree Celsius is given by:

T 1 °F 2 

9

5

T 1 °C 2  32

°R°F459.67

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