Page 380 - Introduction to Marine Engineering

350 Appendix

There are in use certain units which are non-Si but are retained
because of their practical importance. Examples are: time—days, hours,
minutes and speed—knots.
To express large quantities or values a system of prefixes is used. The
use of a prefix implies a quantity multiplied by some index of 10, Some
of the more common prefixes are:
9
I 000 000 000 10 = giga = G
1000000 10 6 = mega = M
3
1000 10 = kilo """"" IV
2
100 10 = hecto = h
10 10' = deca = da
0.1 10" 1 = deci = d
0.01 10~ 2 = centi = c
0.001 10" 3 = milli = m
=
1U~"
0.000001 = 10 - = micro
0.000000001 = 10 r-9 _ nano — n
Example:
10000 metres = 10 kilometres = 10km
0.001 metres = 1 millimetre = 1 mm

Note: Since kilogram is a base unit care must be taken in the use and
meaning of prefixes and since only one prefix can be used then, for
example, 0.000 001 kg = 1 milligram
A conversion table for some well known units is provided in Table
A.2.

Table A.2 Conversion factors
To convert from to multiply
Length
inch (in) metre (m) 0.0254
foot (ft) metre (m) 0,3048
mile kilometre (km) 1.609
nautical mile kilometre (km) 1.852
Volume
3
3
cubic foot (ft ) cubic metre (m ) 0.02832
gallon (gal) litre (1) 4.546
Mass
pound (Ib) kilogram (kg) 0.4536
tonne kilogram (kg) 1016
Force
pound-force (Ibf) newton (N) 4.448
ton- force kilonewton (kN) 9.964