Introduction - Concepts

Last updated at September 16, 2026 by

What we will learn in this chapter?
  • Name of the chapter is — Work, Energy, and Simple Machines.
  • So in this chapter, we will learn about 3 things
    • Work
    • Energy
    • Simple Machines
Lets start with Work first.
What is Work?
  • In easy language — when we apply force on an object and the object moves, we say work is done.
    Example: We lift a bag from the floor to a shelf. We applied force, the bag moved. So we did work.
  • GIF Watch: what is Work Animation for "What is Work". A short looping GIF, three or four beats, drawn in the flat classroom style of the chapter. Beat 1 — In easy language — when we apply force on an object and the object moves, we say work is done. Beat 2 — In technical language — work done = force applied × displacement in the direction of the force. Beat 3 — This we will learn in detail in the next section. Label every arrow and quantity, name the direction each force or motion acts in, and hold the last frame for a moment before the loop starts again.
  • In technical language — work done = force applied × displacement in the direction of the force.
  • This we will learn in detail in the next section.
What is Energy?
  • Energy is the capacity to do work. In easy language — if something has the ability to get a task done, it has energy.
    Example: A moving ball can knock down wickets. So the moving ball has energy.
  • GIF Watch: what is Energy Animation for "What is Energy". A short looping GIF, three or four beats, drawn in the flat classroom style of the chapter. Beat 1 — Energy is the capacity to do work. In easy language — if something has the ability to get a task done, it has energy. Label every arrow and quantity, name the direction each force or motion acts in, and hold the last frame for a moment before the loop starts again.
Where does energy come from in daily life?
  • Energy required to carry out tasks comes from various sources.
GIF Watch: where does energy come from in daily life Animation for "Where does energy come from in daily life". A short looping GIF, three or four beats, drawn in the flat classroom style of the chapter. Beat 1 — Energy required to carry out tasks comes from various sources. Label every arrow and quantity, name the direction each force or motion acts in, and hold the last frame for a moment before the loop starts again.
Activity Source of energy
Walking Food
Fan rotating Electricity
Car moving Fuel
What are Simple Machines?
  • Simple machines are devices that help us perform tasks with less effort and more convenience.
  • They are the building blocks of many everyday machines.
    Example:
    • Pulley — to raise a flag
    • Inclined Plane — to load a box on a truck
    • Lever — seesaw, scissors
    • GIF Watch: what are Simple Machines Animation for "What are Simple Machines". A short looping GIF, three or four beats, drawn in the flat classroom style of the chapter. Beat 1 — Simple machines are devices that help us perform tasks with less effort and more convenience. Beat 2 — They are the building blocks of many everyday machines. Label every arrow and quantity, name the direction each force or motion acts in, and hold the last frame for a moment before the loop starts again.
How are different chapters of physics we have learnt related?
Chapter How it connects
Chapter 4 — Describing Motion We learnt about motion — how objects move
Chapter 6 — How Forces Affect Motion We learnt about how force changes motion of object, and Newton's laws
Chapter 7 — This chapter We track work and energy, which gives a simpler and more powerful way to solve the same problems
Why learn this chapter?
  • Newton's laws work well when the force is constant and simple.
  • But when forces change with time, or act in complicated ways, applying Newton's laws directly becomes difficult.
  • Work and energy give us a simpler and more powerful way to understand such situations.
    Example: A child slides down a curvy slide. The force direction changes at every point. Solving this by Newton's laws is very hard, but with energy it takes just one line.
What will we cover in this chapter?
Topics We Will Study
7.1 Work Done by a Constant Force 7.2 The Work-Energy Theorem 7.3 Forms of Energy 7.4 Mechanical Energy
7.4.1 Kinetic Energy 7.4.2 Potential Energy GPE Gravitational Potential Energy 7.4.3 Conservation of Mechanical Energy
7.5 Power 7.6 Simple Machines
7.6.1 Pulley 7.6.2 Inclined Plane 7.6.3 Lever
Lets start with Topic 7.1-Work Done by a Constant Force.
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