🧪 Class 9 Science – Chapter 11: Work and Energy (कार्य और ऊर्जा) English & Hindi By Grandmaster Bikram Sutradhar | SirBikramSutradhar | BASTRONAUTWAY

Work and Energy
Chapter 11: Work and Energy (कार्य और ऊर्जा)
📘 Chapter Introduction – English Grandmaster Bikram sutradhar bAstronautWay bikram Sutradhar
In this chapter, students explore the scientific definition of work and energy, how to calculate them, and their various forms. The concept of power and commercial unit of energy is also explained clearly, making it easier to understand daily life applications of physics.
📘 अध्याय परिचय – हिंदी
इस अध्याय में आप कार्य और ऊर्जा की वैज्ञानिक परिभाषा, उनकी गणना तथा विभिन्न प्रकारों को समझेंगे। साथ ही, शक्ति (Power) और ऊर्जा की व्यावसायिक इकाई का सरल और व्यावहारिक विवरण भी दिया गया है।
📒 Full Chapter Notes
🔹 1. What is Work? / कार्य क्या है?
- Work is said to be done when a force is applied and it causes displacement.
जब किसी वस्तु पर बल लगाया जाए और वह विस्थापित हो जाए, तो कार्य हुआ माना जाता है। - Formula / सूत्र:
Work = Force × Displacement × cosθ
कार्य = बल × विस्थापन × cosθ - SI Unit: Joule (जूल)
🔹 2. Conditions for Work / कार्य के लिए आवश्यक शर्तें
- A force must be applied. / बल लगाया जाना चाहिए।
- Displacement must occur. / विस्थापन होना चाहिए।
- Some angle must exist between force and displacement.
🔹 3. Types of Work / कार्य के प्रकार
Type | English Definition | हिंदी अर्थ |
Positive Work | Force and displacement are in same direction. | बल और विस्थापन एक ही दिशा में हों। |
Negative Work | Force and displacement are in opposite directions. | |
Zero Work | No displacement or perpendicular force. | विस्थापन न हो या बल लंबवत हो। |














🔹 4. What is Energy? / ऊर्जा क्या है?
- Energy is the capacity to do work.
ऊर्जा कार्य करने की क्षमता है। - SI Unit: Joule (जूल)
🔹 5. Forms of Energy / ऊर्जा के प्रकार
- Kinetic Energy (गतिज ऊर्जा)
- Potential Energy (स्थितिज ऊर्जा)
- Chemical, Heat, Electrical, Light, Sound, etc.
🔹 6. Kinetic Energy (KE) / गतिज ऊर्जा
- Energy possessed by a moving object.
किसी गतिशील वस्तु में मौजूद ऊर्जा। - Formula / सूत्र:
KE = (1/2)mv²
गतिज ऊर्जा = (1/2) × द्रव्यमान × वेग²

🔹 7. Potential Energy (PE) / स्थितिज ऊर्जा
- Stored energy due to position or configuration.
वस्तु की स्थिति के कारण संग्रहीत ऊर्जा। - Formula / सूत्र:
PE = mgh


🔹 8. Law of Conservation of Energy / ऊर्जा संरक्षण का नियम
- Energy can neither be created nor destroyed. It only transforms from one form to another.

🔹 9. Power / शक्ति
- Rate of doing work.
कार्य करने की दर। - Formula / सूत्र:
Power = Work / Time
शक्ति = कार्य / समय - SI Unit: Watt (वॉट)
🔹 10. Commercial Unit of Energy / ऊर्जा की व्यावसायिक इकाई
- 1 kWh = 1000 Watt × 3600 seconds = 3.6 × 10⁶ Joules
1 किलोवाट-घंटा = 3.6 × 10⁶ जूल

✅ MCQs – Multiple Choice Questions (Bilingual)

1️⃣ What is the SI unit of work? / कार्य की SI इकाई क्या है?
🔘 (a) Watt 🔘 (b) Newton 🔘 (c) Joule 🔘 (d) Pascal
✅ Answer: (c) Joule / जूल

2️⃣ Which of the following has only potential energy? / इनमें से किसमें केवल स्थितिज ऊर्जा होती है?
🔘 (a) Running car / दौड़ती कार
🔘 (b) Flying bird / उड़ता पक्षी
🔘 (c) Raised object / ऊँचाई पर रखी वस्तु
🔘 (d) Boiling water / उबलता पानी
✅ Answer: (c) Raised object / ऊँचाई पर रखी वस्तु
3️⃣ Power is the rate of – / शक्ति किसकी दर होती है?
🔘 (a) Speed 🔘 (b) Acceleration 🔘 (c) Work done 🔘 (d) Displacement
✅ Answer: (c) Work done / कार्य

❓FAQs – Frequently Asked Questions (Bilingual)
🔹 Q1. What is 1 Joule of work? / 1 जूल कार्य क्या होता है?
✅ When 1 Newton force displaces an object by 1 meter.
✅ जब 1 न्यूटन बल से कोई वस्तु 1 मीटर विस्थापित हो।
🔹 Q2. What is meant by 1 Watt of power? / 1 वॉट शक्ति का क्या अर्थ है?
✅ Doing 1 Joule of work in 1 second.
✅ 1 सेकंड में 1 जूल कार्य करना।
🔹 Q3. Is energy conserved in all systems? / क्या ऊर्जा सभी प्रणालियों में संरक्षित रहती है?
✅ Yes, energy is always conserved, though it may change its form.
✅ हाँ, ऊर्जा हमेशा संरक्षित रहती है, परंतु यह रूप बदल सकती है।






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Chapter 11: Work and Energy (कार्य और ऊर्जा) SirBikramSutradhar CBSE
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NCERT Solutions
CBSE Class 10 Mathematics (2025) NCERT Syllabus:
CBSE Class 10 Mathematics NCERT Syllabus (2025) – Chapter-Wise List
CBSE Class 10 Mathematics NCERT Syllabus (2025) – Chapter-Wise List
chapter 4. Quadratic Equations
chapter 5. Arithmetic Progressions
chapter 6. Triangles
chapter 7. Coordinate Geometry
chapter 8. Introduction to Trigonometry
chapter 9. Some Applications of Trigonometry
chapter 11. Areas Related to Circles
chapter 12. Surface Areas and Volumes
class 10 science ncert solution
CBSE Class 10 Science (2025) NCERT Syllabus:
CBSE Class 10 Science NCERT Syllabus (2025) – Chapter-Wise List
CBSE Class 10 Science NCERT Syllabus (2025) – Chapter-Wise List
Chapter 1 Chemical Reactions and Equations
Chapter 2 Acids, Bases and Salts
Chapter 3 Metals and Non-metals
Chapter 4 Carbon and its Compounds
Chapter 5 Life Processes
Chapter 6 Control and Coordination
Chapter 7 How do Organisms Reproduce?
Chapter 8 Heredity
Chapter 9 Light – Reflection and Refraction
Chapter 10 The Human Eye and the Colourful World
Chapter 11 Electricity
Chapter 12 Magnetic Effects of Electric Current
Chapter 13 Our Environment
📖 Chapter 12 – Organic Chemistry (Selina Textbook)
Table of Contents:
- 12A. Organic Compounds
- 12B. Hydrocarbons: Alkanes
- 12C. Hydrocarbons: Alkenes
- 12D. Hydrocarbons: Alkynes
- 12E. Alcohols
- 12F. Carboxylic Acids
- Exercise 12 MISCELLANEOUS
- Glossary
- Model Question Paper –
📌 Exercise 12 MISCELLANEOUS – Focus Areas:
🧬 Consolidated practice from the entire Organic Chemistry chapter
🧪 Application-based questions covering alkanes, alkenes, alkynes, alcohols, and carboxylic acids
🧾 Writing structural formulas and chemical equations
💡 Distinguishing reactions, isomer identification, and conversions
📘 Full-syllabus revision to boost conceptual clarity and board exam readiness
Each question in this section is designed to:
✅ Strengthen cross-topic understanding
📝 Prepare students for application-based and reasoning-based questions
🧠 Improve problem-solving speed and exam performance
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