 Units

Measurement is at the heart of science. Without measurements to support or reject a hypothesis, science is simply conjecture - no better than crsytal balls and magic potions. many things can be measured: Consider any object, we can measure its

• mass
• temperature
• volume
• length
• density
• color
• charge
• melting point
• boiling point
• hardness
• molecular weight
•
and so on. The measurement of most quantities have units attached to them. howeverm the matter is compicated by the fact that several units can describe the same quantity, e.g., we can measure length by inches, centimeters, meters, yards, kilometers, miles etc. in order to aviod world-wide confusion, scientists decided to settle on a certain set of units to express basic quantities - the so-called fundamental units

The Fundamental Units
 Mass - kilogram (kg) Length - meter (m) Time - second (s) Temperature - Kelvin (K) Charge - Coulomb (C)

All other units are combinations of these units and are called "derived" units.

 quantity unit SI speed length m/s volume length+3 m+3 energy mass length2/time2 kg m2/s2 density mass/volume kg/m3 force mass length/time2 kg m/s2 pressure mass/length time2 kg/m s2

Volume is an especially important quantity since it can be readily measured. Volume always has the units of a cubic length. the relationship between m3, dl and ml (cc) is readily understood from the diagram below Back to index
C101 Class Notes
Prof. N. De Leon   