Time is the interval between two events. The S.I unit of time is a second (s).

Other units of time include Minute (1min = 60s), Hour (1hr=60min), Day (1day=24hrs), Week (7 days), fortnight (2weeks), Month (1month=30days), Year (1yr=12months), decade, century, and a millennium.

Instruments Used in measuring Time

  • Stop clock
  • stop watch
  • Half life of a radioactive substance eg Carbon – 14
  • Shadows


These are quantities which can be expressed in terms of the fundamental quantities. Besides the seven fundamental quantities, the rest of the Physical quantities’ are derived quantities. Their S.I units are also called Derived units.

Examples of Derived Physical quantities include:

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