Mechanics takes up most of the Physics in the first half of class 11 syllabus. Not only does it form the foundation of Physics, but also lays down the path for future chapters such as waves and even thermodynamics. The play of motion and energy in Mechanics makes it quite interesting. While other chapters sometime take the upper hand, JEE (Advanced) never shies away from presenting tricky questions from mechanics.
Work power energy is the most important chapter when it comes to mechanics, for JEE (Advanced). The chapter is quite tricky and takes a lot of time and devotion on your part to understand and master. But this chapter is a complete gold medal for almost all the questions of the mechanics can be solved by the work power energy approach if you master this topic.
Work Power Energy in JEE (Advanced)
There are few basic theorems which you have to always keep in mind to master the questions from this topic. Make sure to always keep in mind the concepts you have learnt in the previous chapters as they will help you proceed smoothly through the basics of this topic.
Understand the force
The first approach in work power energy problems is to master the lessons of Newton’s law of motions and have an idea about conservative and non-conservative forces. It is only than that you should move ahead to the work-energy chapter. HC Verma is the most helpful book in clearing concepts.
A trick from my personal experience is that if your concepts of the chapter are clear you will be able to solve all the Objective type questions in HC verma without any difficulty because they are mostly concept based. If you are finding it difficult to solve them don’t move forward, clarify your concepts again. After you have solved HCV you can try other books of physics.
Keep the system in mind
The approach to work power energy problems is to define a system. Once you have chosen a system you can identify all the forces in the system and energy going in and out. You always have to remember the fact that “Energy can neither be created nor destroyed, it can only change forms.” Keeping this in mind you can then apply the Work-energy theorem which states that kinetic energy of any body changes by virtue of work done by the “net” force on the body. However, you must remember that this is defined for an isolated system only. Hence the definition of your system is very important.
Balance it out
Always try to balance the kinetic energy, potential energy and the work done. For questions of power, you have the concept that Power is rate of change of work done. Pay special attention to questions on springs and try similar questions from HCV.
Count the variables
An important thing to remember is that while solving mechanics questions, if you are struck in a situation where you have less equations and more unknown variables you can always use the work energy theorem to eliminate one unknown. This is a very strong habit you must inculcate.
In fact, in JEE most questions from work energy chapter are intermixed with other chapters (even with electromagnetism) and you won’t have a clue if the question can be solved by work energy approach. For e.g. a positive charge is thrown on another positive charge with x speed. Find the distance it will travel before coming to rest? To solve such questions, be aware of the type of question and don’t get carried away with the language.
Learn from the past
My advice is to master the concepts of work energy, solve questions on it specifically and then try to solve more and more complex questions that employ more than one concept/topic using mock test papers and previous year papers online. You will have to prepare yourself to identify if a question is a work energy one or not and that’s what will make you successful in mastering this chapter.
Having mastered work power energy, you can tackle almost any problem in mechanics.