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IIT PHASE–2 (Advanced) – PART III Previous IIT-JEE Advanced Questions (Work, Energy & Power)

This section contains authentic IIT-JEE Advanced–level questions based on the chapter Work, Energy and Power. Each solution highlights examiner intention, hidden traps, and topper logic.

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PYQ–1: Block Sliding into Rough Region

Question (IIT-JEE):
A block of mass m moves with speed v on a smooth horizontal surface and then enters a rough region of coefficient of friction μ. Find the distance travelled before coming to rest.

Step-1: Identify method

• Stopping distance
• Constant friction

Correct approach: Work–Energy theorem

Step-2: Energy equation

Initial KE = Work done by friction

½ mv² = μmg s

Answer:

s = v² / (2μg)

IIT Insight: Mass cancels → mass value is a distraction.

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PYQ–2: Particle Thrown Up with Variable Force

Question:
A particle is projected vertically upward with speed u. A constant resistive force f acts opposite to motion. Find the maximum height reached.

Forces involved:

• Gravity (mg)
• Resistive force (f)

Energy balance:

½mu² = mgh + f h

Solve:

h = u² / [2(g + f/m)]

Trap: Using equations of motion fails due to extra force.

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PYQ–3: Pulley with Unequal Masses (Advanced)

Question:
Two blocks of masses m₁ and m₂ (m₂ > m₁) are connected over a smooth pulley. Find their speed after the heavier block descends by height h.

Constraint:

• Same speed magnitude

Energy change:

Loss in PE = (m₂ − m₁)gh

Total KE:

½(m₁ + m₂)v²

Equation:

(m₂ − m₁)gh = ½(m₁ + m₂)v²

Answer:

v = √[2(m₂ − m₁)gh / (m₁ + m₂)]

IIT Trick: No tension, no acceleration required.

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PYQ–4: Particle in a Vertical Circular Loop

Question:
A particle slides down from rest and enters a smooth vertical loop. Find the minimum height required to complete the loop.

Critical condition at top:

• Normal reaction = 0
• v² = gR

Energy equation:

mgh = mg(2R) + ½m(gR)

Answer:

h = 5R/2

Classic IIT favourite – appears in many forms.

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PYQ–5: Variable Force (Graph Based)

Question:
Force acting on a particle varies with position x as shown in the F–x graph. Find the change in kinetic energy from x = a to x = b.

Key rule:

• Change in KE = Area under F–x curve

Answer:

ΔKE = Area between x = a and x = b

IIT Test: Graph understanding, not calculation.

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PYQ–6: Energy Loss & Turning Point

Question:
A particle moving in a potential field loses some energy. How does the turning point change?

Concept:

• Turning point occurs when KE = 0
• Lower total energy → closer turning point

Advanced idea: Turning points are governed by energy equality, not force.

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PYQ–7: Power at an Instant (Advanced)

Question:
A particle moves in a circle with constant speed. Find the instantaneous power delivered by centripetal force.

Analysis:

• Force ⟂ velocity

Answer:

Power = 0

IIT Trap: Motion exists, but energy does not change.

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How IIT Examiners Build These Questions

• Hide energy clues inside wording
• Add unnecessary data
• Break energy conservation subtly
• Test patience & logic

“PYQs are mirrors — study them to see IIT’s mind.”

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.

🔗 Quick Access

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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