About Monday Classes and Problem Sessions

From now onwards we will have the following arrangement for the classes. On Wednesdays and Fridays there will be lectures and on Mondays both the lectures will be reserved for problem solving sessions. Afternoon class we will have tutorials like we had on the last Monday. This means that the problems will be given to you in advance and you have to solve the problems in the class and submit before leaving. In addition one person will be called to solve one question the problem on the board, then next problem will be solved by another person an so on. Others will have the choice of doing it yourself on the paper or of following the solution being worked out on the board. The person who comes to the board will get all the help from me and from Vijay. This will ensure that every one finishes the problems in time. I will call you randomly and will make sure that every one comes to the board at least once and solves at least one problem eventually sometime during the semester. So that is the arrangement for the afternoon session. What you do in the afternoon session is to be submitted. All tutorials will be evaluated and returned. They will make up one unit of assessment of 20 marks.

Morning sessions will be something similar again. We will be solving problems except that you work in groups. Again the problems will be given in advance. What is discussed in the mornings need not be submitted. Last Monday we could discuss only one problem in one hour that is not very efficient. I want this discussion session to be kept under control. So what I suggest is the following. For the morning sessions you work on the problems in groups, discuss and thrash them out in advance. One member of a group will be asked to present solutions of one or two problems, then next a member from some other group chosen randomly will be asked to solve next problem and so on. This is primarily to encourage group activity. You should have some amount of activity discussing Physics among yourself. In India we lack team work. In many organizations people are expected to work as a team. You can see results where ever there is team work. You are expected to solve the problems in advance and come prepared to present solutions. This will also help you to prepare in facing an audience of fifty to sixty and in making a presentation of your ideas to them. The solutions will have to be presented and explained to the class as if you are the teachers and you are explaining it to the class. This part will be evaluated in some way which will be known to you on Monday. The part that should make it interesting for you is that the whole class will be participating in evaluation in the morning sessions. Thus all of you will have to submit a evaluation report for every Monday morning session. This will be considered as group activity and your evaluation will be included for grading. All group activities put together will constitute one unit of evaluation and will carry 20 marks. The problems in the afternoon sessions will be primarily from H.C. Verma's book. The problems in the morning sessions will be on the lectures which I will be giving on Wednesdays and Fridays. The problems in the morning sessions will be similar to what you have solved in the tutorial on rotations and you may not find them in any other book. These problems will be designed to give you supplementary material and provide you help in understanding the lectures.

The other two lectures, on Wednesdays and Fridays will constitute a complete, coherent course by itself, delivered in a logical order. It will be at a slightly higher level. An attempt will be made to consolidate and upgrade what you have already done in 12th standard. Also I will make an effort to present new topics which are not really difficult and are accessible to you

with your level of Mathematics and Physics. Many of these problems do not form part of the text books at 12+ level. Traditionally, the topics, I hope to cover, are included in higher level courses, typically in M.Sc. or B.Sc. honours level courses in Mechanics. What ever can be brought to your level will be included. You do not get worried in the sense that the course will become Hi-Fi or an advanced course. I am only trying to optimise the returns you get for what you already know.

I am attempting to take you to higher level without being too demanding on preparation needed. The results on rotations that have been derived for you is an example, it makes use of only vector algebra and some calculus and does not use any matrices. Normally, I have presented this part of lectures using matrices to M.Sc. students. Only yesterday I discovered that the central result on transformation of coordinates under a rotation can be made much simpler and transparent and now it will be part of an assignment.

I will also make an effort to put a draft of lecture notes in advance on the Moodle Course Site. Later the draft will be modified and will be brought as close to the class room lecture as is possible. I will try to synchronise the lecture delivery in the class and the internet and reduce the phase difference as much as possible. Right now I have already put some lecture notes. Some of them are older versions. Some others are up to date. What I put up on the internet will be almost same, within about 95 to 98\% of what I do in the class. So that you get everything. There may be some improvements and and some 2 to 3 % additional remarks may be added. The only problem is time lag and I will make every effort to minimize it.

Let us then begin with the main topic of discussion In the Newtonian formalism, the Newton's Law play a central role. We have seenthat in order to use the laws to predict the behaviour of mechanical systems, we need to introduce frames of reference. It was also noted that the use of vectors offers important advantages.

Structure of Physical Theories

Here we give an overview of the general structure of formalism of Newtonian Mechanics. There are following four major components to be described in the language of the Newtonian Mechanics.

- State of a physical system
- Physical quantities of the dynamical variables
- The laws of motion or the laws of evolution
- The forces or the interactions

States of Physical system

The idea of {\it state} of a physical system has already been introduced in the previous lecture. One of you had observed that the displacement is a state function and does not depend on the path.

What is meant by state of a system? If you are already familiar with the concept I will build upon your understanding.

**Dialogue with students**

### Dialogue with students

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### Dialugues with students

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