The chapter for Units and Dimensions are collectively called Dimensional Analysis. This basically means that it involves the analysis of the different kinds of relationships between the mechanical physical quantities. How do we do it? This is done by taking the physical quantities and their relationship. Here what we do is identify the base quantities and these are mass, time, length or electric current. This is the very first step where we take the base quantities and thus the conversion of one physical quantity to another is easier method. When we take physical quantities which are not same and these are known as incommensurable physical quantities. The dimensional analysis is also known as unit factor method. When we take these units and put them into an equation then one side of the equation should be same to the other side of the equation. This process is called dimensional homogeneity. This is important for the process of dimensional analysis. This process also serves to establish two physical quantities if they are measured under the functions of addition, subtraction and comparability and equality.

Any physical quantity which can be measured or compared can use the basic functions but it will be meaningless to use some basic functions for two physical quantities that cannot be measured or compared. Like two different physical quantity like kilogram and hours. These two cannot be compared or even be made into one component because the basic rules of arithmetic cannot be used here.

Some of the important concepts for the Units and Dimensions Measurements chapter are: The parallax method of measurement of large distances which is nothing but the displacement of the body position when it is viewed along two lines and it thus calculated by the angle or semi-angle of the inclination made by the two lines. This main concept lies in the distance between the two viewpoints.

Another concept is the measuring the small distances – When we measure the distance between very few distances like for example in the size of the molecules the microscope is used and thus this will include the electron beam which is controlled by some magnetic fields.

Here the electron microscope is used to resolve the atom and molecule size by using a tunnelling microscope. This thus makes it easier to count the distance between the molecules.

Concrete numbers and base units: Many units of physical measurements can be expressed in terms of concrete numbers which is a numerical quantity and it has a unit. Thus one quantity is expressed in some different dimensional unit. Example- Speed is an combination of length and time. To express speed for an engine or system we need to express it in terms of how far it can go or work and in how much of time frame can it be done. If we take a set of base units for a measuring system for a chosen set of units thus the result is that none of it can be expressed as a combination of the other. Example – units of length and time are the base units. However volume is a derived unit since they can be factored in to the base units of length. Derived units are also known as compound units.

__How to Set Pace preparation for NEET/AIIMS:__

To basically study for the NEET or AIIMS a thorough study schedule is important. Whatever be the concept or unit or chapter it can be completed if the following are regarded during the time of preparation:

- Have a strict study schedule for any kind of exam is important and thus this can foster a sense of confidence since equal time is demanded by each of the chapter. This is also important since for an exam like NEET the emphasis lies in all the three subjects.
- Giving equal time to all the three subjects. This is equally important since all the subjects have very tough concepts one needs to understand and prepare for the exam.
- Going through previous years question papers- Doing NCERT and referring some of the important books will be useful especially the previous years question papers for the exam.
- Getting the concepts clear is important for any student for any kind of concept for any subject. We know that practice makes a man perfect hence for subjects like Physic and Mathematics and Chemistry also we have to make an effort to make the concept clear before we can attempt complicated problems and discussions.

Important multiple choice type question:about Match List-I with List-II and select the correct answer using the codes given below the lists