the quantities by meals of which we describe the law of physics are known as physical quantities.
in order to measure a physical quantity we as you my certain magnitude of this quantity a standard and call its unit of that quantity to express the measurement of any physical quantity two thing must be mentioned.
- the unit in which the quantity is measured.
- the numerical value which do not the magnitude of that quantity in term of the choosen unit.
For Example -:
- when we say that the length of a road is 20 m its mean that the unit of length is matter and the length of rod 20 time magnitude of metre.
- in other number the numerical value of physical quantities inversely proportional to its unit if N1 and N2 be the numerical value of a physical quantity into different unit u1 and u2 then