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CHAPTERS BY WACEK KIJEWSKI

# CHAPTER III:  Physical Quantities, Units, Symbols and
Prefixes

Many experiments carried out in physics and chemistry are quantitative. They involve assigning numbers to length, mass, time, current, density etc. The thing which can be measured is called the physical quantity. Each quantity has its own symbol, a letter. Most quantities have units and each unit has a name and its own symbol. The symbol for a unit is either a letter or a series of letters. 

Some quantities are unitless, i.e. they are represented only by a number. The number, in turn, represents how much the quantity is greater or smaller than a reference or standard quantity. Examples of unitless quantities: magnification, relative density, efficiency.

Units, especially SI units, are often used with prefixes indicating multiples or submultiples. A prefix has its own symbol too. The list of prefixes used with SI units is presented in Table 1.

Do you like anecdotes, interesting and challenging problems, fun facts, puzzles, jokes related to metric system and measurement? Read them in the 2006 on-line edition of "SI Units, Conversion and Measurement Skills",186 pp.

Wacek Kijewski
Metric Fun
"SI Units, Conversion and Measurement Skills"
PO Box 2358 George 6530 South Africa
tel/fax: +27 44 884 0486

About the Author

Wacek Kijewski: born in Poland, studied electronics, telecommunication, acoustics and pedagogy. He taught science in Poland, Hungary and became Lecturer and Principal Tutor in Nigeria and Botswana.
Mr. D.D. Kuhlmann, Ag Registrar, University of Botswana (UB): “Dr W. Kijewski has performed his duties very satisfactorily and proved that he is an excellent teacher with substantial relevant experience. He has an admirable character which coupled with his professional integrity enabled him to established an excellent rapport with students.”

Dr. L.S. Molema, English Dept., UB: “Students speak warmly of him, especially his capacity for making them understand and feel confident in a subject that they had previously been inadequately prepared for and were therefore scared of. I have just finished editing the proofs of his new book: “S I Units, Conversion and Measurement Skills” in which his teaching style, so popular with his students, is evident.”

Donate to support this site

Your donation will help us maintain and update the pages with better unit conversions and build new features.
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