Measurement and Physical Quantities

Measurement is comparison of one thing with another thing that has already been a standard where an observation is needed. In physics, Measurement is ratio of one physical quantity with another physical quantity that has standard. Measurement is needed in our daily life but sometimes we don’t realize that we have already measured, for example: We know the tallest boy in the class or the most generous person in the school. We can say that almost all occupations need to measure such as a carpenter who will make a shelf or a table and an automotive designer who will make a good design of a car, etc.

Physical quantity is a quantity that can be measured. If it could not be measured, it was not a physical quantity such as sweetness, virtues (discipline, kindness, etc), beauty, wildness, etc. A physical quantity has a SI unit (System International unit). SI Unit is a unit that is accepted by whole countries in the world as a standard unit.

TWO KINDS OF PHYSICAL QUANTITIES
There are two kinds of physical quantities:
1)Base Physical quantities
This physical quantity is very basic and not derived from other physical quantities. There are 7 base physical quantities, as follow :

















2)Derived physical quantities
Derived physical quantities are quantities derived from base physical quantities. For example:

















STANDARD FORM NUMBERS


Sometimes we can find kind of number which is too long to write for example 1.000.000.000 to simplify we use standard form number as 10^9 or prefix as 1 Giga.
















There are some rules to use standard form number :
* The number should have more than two zeros or thousandth up. If it is still hundredth, we don’t need to convert into standard form. See examples below:
100 No need to convert into standard form number.
1.000 10^3
10.000 10^4
100.000 10^5
0,01 No need to convert into standard form number.
0,001 10^–3
0,0001 10^–4
*To convert usual numbers into standard form numbers, we must let the number between 1 - 10. There are two ways to convert according to the numbers, as follows:
a)if the number is more than 1
We count how many zeros that the number has or how many steps we moved the comma of the numbers. See examples below:
-1.000 has three zeros so that we can write as 10^3 in standard form number.
-10.000 = 10^4
-11.000 = 1,1 x 10^4
-27.000 = 2,7 x 10^4
-340.000= 3,4 x 10^5
b)if the number is less than 1
We count how many steps we moved the comma of the numbers. See examples below:
-0,001 = 10^–3
-0,0001 = 10^–4
-0,004 = 4 x 10^–3
-0,0007 = 7 x 10^–4
-0,0025 = 2,5 x 10^–3
*Operation in standard form numbers.
Multiplication
Add the power of the standard form numbers and multiply the numbers in front of the cross sign. For examples:
-10^3 x 10^4 = 10^(3 + 4) = 10^7
-2 x 10^3 x 3 x 10^4 = 2 x 3 x 10^(3 + 4) = 6 x 10^7
Division
Subtract the power of the standard form numbers and multiply the numbers in front of the cross sign. For examples:
-10^8 : 10^3 = 10^(8 - 3) = 10^5
-(8 x 10^9) : (2 x 10^6) = 4 x 10^(9 - 6) = 4 x 10^3