It is just a chapter which makes us remember some ideas which were studied in earlier classes. 

Units,Dimensions and Error analysis mainly depends on our mathematical skills.It is easy when you just try to understand the main concepts first and should brush up our mathematical approach to various problems.

First of all, we should know about the title itself. What are units? Unit is the standard used to measure a physical quantity by comparing the value of the quantity to the unit.There are different types of unit systems in the world. SI (Systeme Internationale d' Units)  is currently used as the standard unit system.

Dimensional Analysis is the powers to which the fundamental quantities are to be raised in order to represent a physical quantity.

There are lot of advantages and disadvantages of dimensional analysis, 


1) To check the correctness of an equation.
2) To convert a unit from one system to another.
3) To derive the correct relationship between physical quantities.


1) In mechanics, this method is not suitable when the physical quantity depends on more than three other quantities.
2) Doesn't tell about dimensionless quantities like numbers.
3) Cannot be employed if RHS of equation contains more than one term.
4) Difficult to guess the parameters on which the physical quantity depends.

If I am measuring a thing, I would have to report the accuracy of my data and in order to report it I have to fully communicate the significance of my findings. The simplest way of expressing the accuracy of the measurement is to omit all the digits in a number which I have no information. The number of digits in which I have confidence is its significant figures.

In any measurement there is a chance of change from the actual measurement. This is a error.

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