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1. Definition of Work I

In ordinary conversation the term ‘work’ may mean a wide variety of activities, but to a physicist its use is far more restricted. Does a weightlifter do any work while supporting a barbell on his shoulder? Does a passenger do any work in pushing the wall of a running train compartment? Can work done by a force be negative, or path-independent? How to compute the work done by a variable force such as spring force? The video lecture “Definition of Work” answers some of these questions, and more.

2. Definition of Work II

3. Work done by Varying Force

4. Work done by Spring Force

5. Concept of Energy and Derivation of Work-Energy Theorem

When a particle changes position under several forces, the total work done on the particle is the algebraic sum of the works done by individual forces. The kinetic energy of a particle is the energy due to its motion. What is the relation between total work and kinetic energy? Does this relation depend on the frame of reference? When a coin is tossed up in air, why does its speed decrease and then increase again? Why does a particle under centripetal force maintain constant speed? The video lecture “ Work-Energy Theorem” answers some of these questions, and more.

6. Potential Energy

7. Problems on Kinetic Energy and Work-Energy Theorem

8. Power

9. Potential Energy Function

10. Principle of Conservation of Mechanical Energy and some Applications

11. More Applications of Mechanical Energy conservation Principle

12. Problems on Principle of Mechanical Energy Conservation

13. Equivalence of Mass and Energy

14. Conservative and Non-Conservative Forces

The potential energy of a system is usually defined as the energy possessed by the system due to its configuration. However, for a more refined definition, one must know the difference between conservative and non-conservative forces. Can the work done by a force be independent of the open path followed by a particle? If yes, what is the work done if the particle follows a closed path? Is spring force always conservative? Is the force of friction always non-conservative? The video lecture “ Conservative and Non-Conservative Forces” answers some of these questions, and more.

15. Problems on Conservative and Non-Conservative Forces

16. Conservative Force from Potential Energy Function and Energy Diagram

17. Problems on Principle of Mechanical Energy Conservation

18. Principle of Conservation of Energy and Some Applications

19. Principle of Conservation of Mechanical Energy

For an isolated system of particles interacting only through conservative forces, the sum of kinetic and potential energies remains constant. This conservation principle is the foundation of ‘energy method’, just like Newton's second law is the foundation of ‘dynamical method’. What is the speed gained by a pebble thrown from a given height? What is the speed gained by a block sliding down a wavy incline? How does the speed of a pendulum bob vary with position? With what speed does a block at the end of a stretched spring return? The video lecture “Examples of Principle of Conservation of Mechanical Energy” answers some of these questions, and more.