Quantities and Units

Quantities, Symbols and Units

Physics often involves looking at quantities:

  • A symbol is used to represent a quantity (v for speed)

  • A unit is what the quantity is actually measured in (m/s for speed)

Base Units and Derived Units

There are seven base units used in physics from which all the others can be derived:

  • Base units are the metre, kilogram, second, ampere, kelvin, mole and candela

  • Derived units include metres per second and kilograms per cubic metre

Unit Prefixes

It is often more convenient to add a prefix to very small or very large quantities.

Converting Units: Example A

A worked example where units are converted from one form to another.

Converting Units: Example B

Here we convert units for area and volume.

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