CBSE · Class 9 · Science · Chapter 7

Work, Energy, and Simple Machines

Understand work, energy, power and how simple machines make everyday tasks easier.

13 lessons 60 min
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Lessons in this chapter

  1. 1Work Done by a Constant ForceWork gets a strict definition, so carrying three bags finally becomes measurable bragging.
  2. 2When Is Work Done Equal to Zero?A wall can exhaust your muscles while stubbornly receiving zero mechanical work.
  3. 3The Work-Energy TheoremEnergy changes hands whenever work steps into the conversation.
  4. 4Forms of Energy and Mechanical EnergyEnergy changes costumes constantly, but it never forgets the job it came to do.
  5. 5Kinetic EnergySpeed enters the formula once and somehow leaves wearing a square.
  6. 6Potential EnergyA stretched band looks still, but it is quietly saving trouble for later.
  7. 7Gravitational Potential EnergyHeight gives an object stored energy without making it look any more impressive.
  8. 8Conservation of Mechanical EnergyPotential energy and kinetic energy keep trading places without losing the total receipt.
  9. 9PowerThe stairs do not care how fast you climb them, but power certainly does.
  10. 10Simple Machines and PulleyA pulley cannot erase work, but it can persuade gravity to accept a more convenient direction.
  11. 11Inclined PlaneThe ramp wins against the vertical lift by taking the scenic route.
  12. 12LeverMove the fulcrum, lengthen the arm, and suddenly the heavy object starts negotiating.
  13. 13Chapter Summary and PracticeWork, energy and machines gather for one final meeting, and even the pulley has homework.
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