Work and Energy പ്രവൃത്തിയും ഊർജവും
The chapter opens at a huge dam in the hills, like the Idukki dam whose water runs the Moolamattom power house. A boy says: “Electricity is produced in large quantities using the water in this dam.” His friend asks: “How does the water get so much energy?” By the end of this chapter you will answer her. You will learn what physicists mean by work (പ്രവൃത്തി) and how to measure it in joules. You will meet energy (ഊർജം) – the capacity to do work – and its two mechanical kinds, potential energy (സ്ഥിതികോർജം) and kinetic energy (ഗതികോർജം). You will see that energy is never created or destroyed, only changed from one form to another, and you will finish with power (പവർ), the rate of doing work, measured in watts. This interactive, animated self-study guide starts from the basics – force, displacement, units and squares – explains every idea with Kerala examples, answers every textbook question, and ends with a revision sheet and a model test.
The chapter in one picture
Follow the orange drop: it stands for 1 kg of water. High up in the reservoir (റിസർവോയർ) behind the dam (അണക്കെട്ട്) it is not moving, but it is 100 m above the turbine, so it has potential energy (സ്ഥിതികോർജം): Ep = m g h = 1 × 9.8 × 100 = 980 J. As it rushes down the penstock (പെൻസ്റ്റോക്ക്) it loses height and gains speed: its potential energy turns into kinetic energy (ഗതികോർജം). The purple and red bars always add up to the same 980 J. At the bottom it is moving at about 44 m/s (v² = 2 × 9.8 × 100 = 1960). It spins the turbine (ടർബൈൻ), which turns the generator (ജനറേറ്റർ), and the energy leaves as electrical energy (വൈദ്യുതോർജം) to light the bulbs. Not a joule is created or destroyed – it only changes form (ഊർജപരിവർത്തനം). (Idealised: friction in the pipe and losses in the machines are ignored; a real station turns most, but not all, of the energy into electricity. In a real penstock the pipe is full of water, and the water's pressure also helps carry the energy down – the total is the same.)
How to use this guide
🎬 Watch the animations
Cranes lift containers, coconuts fall, pile drivers hammer and turbines spin, one step at a time. Press Next ▶ or ▶▶ Auto play.
🧪 Do the virtual experiments
Push wheelchairs, roll a tin into a block, race your friends lifting books and watch energy bars rise and fall. Every number is worked out with real physics (W = F s, Ep = m g h, Ek = ½ m v², P = W/t). Where the textbook activity has no fixed numbers, the guide uses sample readings.
✍️ Try before you see
Every numerical is laid out the exam way: Given → Formula → Substitution → Answer. Use 💡 Show a hint first and work in your notebook. Then open ✅ Show final answer.
📖 Textbook words
Purple മലയാളം words are the exact terms used in your textbook (pages 107–130), so you can match this guide with your book and write answers in either language.
Learning path
Follow the pages in order. If you are already confident with force and displacement, units and powers of ten, squares and forms of energy, you can skim pages 1–4. Still try their quizzes, because the chapter uses these ideas on every page.
Quick glossary (Malayalam ↔ English)
| Textbook term | English | Meaning |
|---|---|---|
| പ്രവൃത്തിയും ഊർജവും | Work and energy | The chapter title |
| പ്രവൃത്തി | Work | Done when a force displaces an object in the direction of the force: W = F s |
| ബലം | Force | A push or a pull, measured in newtons (N) |
| സ്ഥാനാന്തരം | Displacement | The straight-line change of position, with its direction, in metres |
| ബലത്തിന്റെ ദിശ | Direction of the force | The way the push or pull acts |
| ഘർഷണബലം | Friction | The force between surfaces that opposes sliding or rolling |
| ഗുരുത്വാകർഷണബലം / ഭൂഗുരുത്വാകർഷണബലം | Gravitational force / force of gravity | The Earth's downward pull on an object, m g |
| ഗുരുത്വാകർഷണത്തിനെതിരായ പ്രവൃത്തി | Work against gravity | The work done in lifting an object: W = m g h |
| പോസിറ്റീവ് പ്രവൃത്തി / നെഗറ്റീവ് പ്രവൃത്തി | Positive / negative work | Displacement along / opposite to the force |
| ജൂൾ (J) | Joule | The unit of work and energy: 1 J = 1 N × 1 m |
| ന്യൂട്ടൺ മീറ്റർ | Newton metre | N m – another name for the joule |
| ഊർജം | Energy | The capacity to do work, in joules |
| ഊർജരൂപങ്ങൾ | Forms of energy | Electrical, mechanical, heat, chemical, light, sound, solar, nuclear… |
| വൈദ്യുതോർജം · യാന്ത്രികോർജം · താപോർജം | Electrical · mechanical · heat energy | Three forms you will meet on almost every page |
| രാസോർജം · പ്രകാശോർജം · ശബ്ദോർജം · സൗരോർജം | Chemical · light · sound · solar energy | Energy stored in food and fuels; energy of light, of sound, and from the Sun |
| സ്ഥിതികോർജം | Potential energy | Energy due to position or configuration; Ep = m g h |
| സ്ഥാനം മൂലമുള്ള സ്ഥിതികോർജം | Potential energy due to position | A coconut on the tree, water in a tank |
| കോൺഫിഗറേഷൻ മൂലമുള്ള സ്ഥിതികോർജം | Potential energy due to configuration | A drawn bow, a compressed spring, a bent pole |
| ഗതികോർജം | Kinetic energy | Energy due to motion; Ek = ½ m v² |
| ഊർജപരിവർത്തനം | Energy transformation | Change of energy from one form to another |
| ഊർജസംരക്ഷണ നിയമം | Law of conservation of energy | Energy can neither be created nor destroyed |
| കലോറി / കിലോകലോറി | Calorie / kilocalorie | Food-energy units: 1 cal = 4.2 J, 1 kcal = 4200 J |
| ജലവൈദ്യുതനിലയം | Hydroelectric power station | A power station run by falling water, like Moolamattom |
| റിസർവോയർ / അണക്കെട്ട് | Reservoir / dam | The lake of stored water / the wall that holds it back |
| പെൻസ്റ്റോക്ക് | Penstock | The big pipe that carries water down to the turbine |
| ടർബൈൻ / ജനറേറ്റർ | Turbine / generator | The wheel turned by the water / the machine that turns rotation into electricity |
| പവർ | Power | Work done per second: P = W/t |
| വാട്ട് (W) | Watt | The unit of power: 1 W = 1 J/s |
| കുതിരശക്തി (HP) | Horsepower | A unit of power for motors and vehicles: 1 HP = 746 W |
| അദിശ അളവ് / സദിശ അളവ് | Scalar / vector quantity | Has only a size (work, energy, power) / has a size and a direction (force, displacement) |
| ഗ്രാഫ് | Graph | A picture of how one quantity changes with another |
| പ്രവർത്തനം · സയൻസ് ഡയറി | Activity · science diary | Things to do, and the notebook where you write what you observed |
| വിലയിരുത്താം · തുടർപ്രവർത്തനങ്ങൾ | Let us assess · extended activities | The end-of-chapter questions and projects (solved on pages 12–13) |
🌐 Explore online (optional)
Everything in this guide works offline: each page is a single file with no internet needed. Some pages also have blue “🌐 Explore online” boxes. They link to free websites and interactive simulations, including PhET simulations such as “Energy Skate Park”, which your textbook mentions. Those links need internet and open in a new tab. All of them are collected in the resources hub on page 14.
- 📄 Physics Tutorial - Work and Energy The Physics Classroom
Hub page for the whole chapter - work, energy, power and conservation in one place. - 📄 Chandrayaan-3 Details ISRO
India's Moon mission - the Vikram lander had to control its energy carefully for a soft landing.
Made for self-learning. Works offline – every page is a single file. Study material prepared by Claude for Madhu's family study folder, October 2026.