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Lesson 5 – Work, Energy and Power All-Angle Notes (From Previous Questions)

This section consolidates all recurring exam angles from previous Intermediate and competitive questions. Every concept here has appeared in exams in different forms.

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ANGLE 1: Definition-Based Questions

Repeated Question Pattern:

• Define work
• Define energy
• Define power
• What is kinetic energy?

Exam-Ready Definitions:

• Work: Work is said to be done when a force acting on a body produces displacement in the direction of the force.
• Energy: Energy is the capacity of a body to do work.
• Power: Power is the rate of doing work.
• Kinetic Energy: Energy possessed by a body due to its motion.

Examiner expectation: Exact textbook language → full marks.

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ANGLE 2: Sign of Work (Very Common)

Previous question forms:

• Give examples of positive, negative and zero work
• Why is work done by friction negative?
• Why is centripetal force doing zero work?

Key Points:

• Positive work → Force and displacement same direction
• Negative work → Opposite directions
• Zero work → Perpendicular force or zero displacement

Standard examples:

• Gravity on falling body → Positive work
• Friction on moving body → Negative work
• Centripetal force → Zero work

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ANGLE 3: Formula-Driven Questions

Frequently asked formulas:

• Work = F s cosθ
• Kinetic Energy = ½ mv²
• Power = Work / Time
• Power = Fv

Exam Pattern:

• Direct numerical substitution
• Formula writing carries marks

Tip: Even if final answer is wrong, writing formula gives partial marks.

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ANGLE 4: Derivation-Based Questions

Most repeated derivations:

• Derivation of kinetic energy
• Work–energy theorem

Expected structure:

1. Assume body of mass m
2. Use equations of motion
3. Relate force, displacement, velocity
4. Conclude with final expression

Important: Do not skip steps — marks are step-wise.

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ANGLE 5: Numerical Problems (High Frequency)

Common numerical types:

• Finding kinetic energy
• Work done by force
• Finding power
• Energy change questions

Standard solution format:

1. Given
2. Required
3. Formula
4. Substitution
5. Answer with unit

Board rule: Step-wise presentation = higher marks.

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ANGLE 6: Conceptual Reasoning Questions

Asked as:

• Why does a fast-moving body have more kinetic energy?
• Why is power important?
• Why is energy conserved?

Answer approach:

• State concept
• Support with formula
• Give real-life example

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ANGLE 7: Power-Related Traps

Repeated confusion areas:

• Average power vs instantaneous power
• Power at constant velocity
• Power when force ⟂ velocity

Key facts:

• At constant velocity → net force = 0 → power = 0
• Instantaneous power = Fv

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ANGLE 8: Assertion–Reason Questions

Typical themes:

• Work done by friction
• Power depends on time
• Kinetic energy depends on velocity

Strategy:

• Check assertion independently
• Check reason independently
• Then check explanation link

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FINAL EXAM CONSOLIDATION

• This chapter is formula + logic based
• Numericals are scoring
• Definitions must be precise
• Energy method simplifies problems

“If you understand energy, mechanics becomes easy.”

Work, Energy & Power – Complete Physics Library

This is the MASTER LIBRARY PAGE for the complete chapter Work, Energy and Power, prepared for Intermediate, IIT-JEE (Main & Advanced), NEET and competitive exams.

All concepts are explained from basic to IIT level, including theory, derivations, numerical problems, objective questions, previous year questions, tough IIT problems, tricks and cautions.

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📚 Complete Lesson Index (Part 1 – Part 39)

1. Part 1 – Introduction to Work
2. Part 2 – Types of Work
3. Part 3 – Variable Force & Graphs
4. Part 4 – Kinetic Energy
5. Part 5 – Work–Energy Theorem
6. Part 6 – Potential Energy
7. Part 7 – Conservative Forces
8. Part 8 – Mechanical Energy
9. Part 9 – Power
10. Part 10 – Power Applications
11. Part 11
12. Part 12
13. Part 13
14. Part 14
15. Part 15
16. Part 16
17. Part 17
18. Part 18
19. Part 19
20. Part 20
21. Part 21
22. Part 22
23. Part 23
24. Part 24
25. Part 25
26. Part 26
27. Part 27
28. Part 28
29. Part 29
30. Part 30
31. Part 31
32. Part 32
33. Part 33
34. Part 34
35. Part 35
36. Part 36
37. Part 37
38. Part 38
39. Part 39 – Final IIT Tough Problems & Solutions

Prepared by: Shaktimatha Learning 🌱

Strong Concepts • Smart Practice • Exam Success