Numbers and Units

10m = a physical quantity

Physical Quantities are made up of two parts :-
- number
- unit

Units:

Giga = 10^9
Mega = 10^6
Kilo = 10^3
Deci = 10^(-1)
Centi = 10^(-2)
Milli = 10^(-3)
Micro = 10^(-6)
Nano = 10^(-9)

There are many Units so a common system of units is used called the SI Units.

SI Units = base units for measuring mass, time, length .etc.



Mass

SI Unit = kg

- affects how objects behave in two ways

i) The greater the mass of an object, the stronger the gravitational pull Earth has on it.
ii)The greater the mass, the greater is the resistance to change in motion.


Time

SI Unit = second

1 second = the frequency of an oscillation in the nucleus of a caesium atom


Length

SI Unit = m

1 metre = The length traversed by light in 1/299792458 th of a second.


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