# THE SI SYSTEM

SI is an abbreviation for Systeme International and is a metric system of units that is being adopted internationally for all scientific and engineering work. This brief presentation presents only the aspects of the system pertinent to this text.

Names of International Units
“I N/m2= I Pascal, denoted by Pa. |

DEFINITIONS

newton (N) The newton is the force that gives a mass of 1 kg an acceleration of 1 m/s/s.

joule (J) The joule is the work done when the point of application of 1 N is displaced a distance of 1 m in the direction of force.

watt (W) The watt is the power that gives rise to the production of energy at the rate of 1 J/s.

Conversion Factors

Multiply By To Get

Newtons (N)

Meters (m)

Kilograms (kg)

Kilograms per cubic meter (kg/m3) Kilowatts (kW)

Pascals (Pa)

Pascals (Pa)

Meters per second (m/s)

Meters per second (m/s)

MISCELLANEOUS

g = 32.2 ft/sec2 = 9.81 m/s2 at sea level °K = °С+ 273.19 °R = °F +459.7 °С = (°F – 32)(5/9)

Universal Gas Constant (p = pRT)

R = 1716 ft2/s2/°R = 287.0 m2/s2/°K

PREFIXES

The names of multiples and submultiples of SI units may be formed by application of the following prefixes.

Factor by which unit is multiplied |
Prefix |
Symbol |

1012 |
tera |
T |

109 |
giga |
G |

106 |
mega |
M |

103 |
kilo |
к |

102 |
hecto |
h |

10 |
deka |
da |

10~‘ |
deci |
d |

10~2 |
centi |
c |

10~3 |
milli |
m |

10~6 |
micro |
p |

io-9 |
nano |
n |

10~12 |
pico |
p |

10’15 |
femto |
f |

10 18 |
atto |
a |

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