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Tham khảo tài liệu 'intro to marine engineering 2 2011 part 13', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 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 1000000000 109 giga G 1000000 106 mega M 1000 103 kilo k 100 102 hecto h 10 10 deca da 0.1 10 deci d 0.01 10-2 cent c 0.001 10 3 milli m 0.000001 10 6 micro M- 0.000000001 10 9 nano n Example 10000 metres 10 kilometres 10 km 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 cubic foot ft3 cubic metre m3 0.02832 gallon gal litre 1 4.546 Mass pound lb kilogram kg 0.4536 tonne kilogram kg 1016 Force pound-force Ibf newton N 4.448 ton-force kilonewton kN 9.964 Appendix 351 To convert from to multiply Pressure pound-force per square inch Ibf in2 kilonewton per square metre kN m2 6.895 atmosphere atm kilonewton per square metre kN m2 101.3 kilogram force per square centimetre kgf cm2 kilonewton per square metre kN m2 98.1 Energy foot pound-force joule Q 1.356 British Thermal Unit BTU kilojoule kJ 1.055 Power horsepower hp kilowatt kW 0.7457 metric horsepower kilowatt kW 0.7355 Engineering terms The system of measurement has been outlined with an introduction to SI units. Some of the common terms used in engineering measurement will now be described. Mass Mass is the quantity of matter in a body and is proportional to the product of volume and density. The unit is the kilogram and the abbreviation used is kg . Large quantities are often .
