Approaching Rotational Mechanics for JEE Advanced:
As far as physics of JEE-Advanced is concerned, mechanics forms a major chunk of the questions asked and of that rotational mechanics is generally considered to be the most important. Having said that, this topic is generally a night-mare for students and one of the favorite topic of examiners as they will be able to test you in all the concepts that you had learnt previously right from the basic formula F=ma to the energy conservation equation. They’ll mix up these concepts in questions which will be intimidating or fascinating to read and when it comes to solving them many scratch their heads in the unsuccessful attempt. In order to excel in this topic, one must be ready to devote sufficient time and efforts. Here are some points that I feel should help you in your preparation of rotational mechanics.
Strong Foundation :-
Rotation is seen as one of the most important topic of mechanics which also demands a good understanding of previous topics like Kinematics, NLM, etc. So make sure to have good command over the previously learnt topics, namely, Work, Power and Energy, Center of Mass, Momentum Conservation. To be able to draw FBDs is of utmost important, sometimes a neat and correct FBD is the only step you’ll require to find the solution. A small mistake in that and the whole method goes wrong, so make sure you know that well.
Focus on concepts :-
This topic is vast when compared to the other topics of mechanics and consists of a lot of concepts. Torque, moment of inertia, angular momentum, pure rolling and slipping conditions, etc. are some of it. Best way to gain command over all of these is to go one concept at a time and then start mixing them up whenever you seem to become comfortable. I’ll suggest you to solve questions from H C Verma to get a clear picture of the application of concepts.
Imagination and Practical Approach :-
Now this is another important ingredient you’ll need while solving problems. You need to form a mental picture of the problem as it becomes quite easy then to recognise the different forces acting, draw the FBD and you’ll get a rough idea on how the body will behave in the given conditions. Rather than just mugging up those scary force equations try to understand what it implies. You can get some more help on this here.
Books to be referred :-
This is one point which you’ll have to figure out well because the types of question that you’ll solve will be a deciding factor of your score in rotational mechanics. As mentioned earlier, I’ll suggest NCERT textbook and Concepts of Physics by H.C. Verma to start with. Once you are comfortable with the different concepts involved you might want to try the book Problems in general Physics by IE Irodov which will test your concepts pretty well. But the questions of this book are quite difficult so go for it only if you are confident enough, if not then there are loads of other books such the ones by DC Pandey, Arihant which contains ample questions of the pattern that is asked in JEE.
Problem Solving :-
In mechanics, questions asked will be mostly numerical based so you need to have a perfect balance between the conceptual knowledge and problem solving efficiency. While solving problems, focus more on the quality of questions rather than quantity (that doesn’t mean you should solve specific limited number of questions, solve as many as you can and whatever time permits). You can’t master any topic of mechanics within 2-3 weeks so make sure you allot sufficient time from now itself and start practising around 20-30 questions per week and keep increasing them as you progress.
The most important aspect of mechanics is practice and your ability to concentrate on the concepts and apply it in exams. Questions from rotation in JEE may seem difficult at first look but they are not, the key to arrive at the solution will always be a small concept which you should be able to figure out. Once you figure out that, then the problem should be a cake-walk for you. To know more about mechanics of JEE Advanced refer this article.
All the best!