Lesson 6 – Centre of Mass & System of Particles

PHASE–3 · PART–4
Time-Pressure Mock Analysis & Speed Control

This part trains students to score maximum marks from Centre of Mass questions under real IIT-JEE time pressure.

1️⃣ The 30-Second Rule (Critical)

In mock or exam:

✔ If method is clear within 30 seconds → SOLVE
✔ If method is not clear → SKIP & MOVE

Never fight a question blindly.

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2️⃣ Question Selection Strategy (COM-Specific)

🟢 FIRST ATTEMPT:
• Explosion / collision questions
• System push / pull problems
• Direct COM law MCQs

🟡 SECOND ROUND:
• Integer type with light calculation
• Frame-based questions

🔴 LAST / OPTIONAL:
• Lengthy story problems
• Heavy algebra with little concept gain

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3️⃣ Speed Killers (Must Avoid)

❌ Writing equations for each particle
❌ Calculating when law alone is enough
❌ Ignoring frame mention (lift/train/wedge)
❌ Re-checking easy questions multiple times

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4️⃣ How Toppers Solve Faster (Real Insight)

✔ They don’t calculate early
✔ They mentally apply ΣF = M a_cm
✔ They predict answer range before solving
✔ They eliminate options before full math

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5️⃣ Accuracy Protection Technique

Before marking answer, ask:

✔ Did I ignore internal forces correctly?
✔ Did I assume correct frame?
✔ Does answer violate COM law?
✔ Is sign (+/–) logical?

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6️⃣ Mock-Test Reflection (After Exam)

✔ Did I waste time on hard COM question?
✔ Did I miss easy COM scoring question?
✔ Did confusion come from frame or force?

Improvement comes from analysis, not from solving more questions blindly.

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🏁 PHASE–3 · PART–4 CLOSURE

This part ensures that Centre of Mass becomes a time-saving topic, not a time-eating one.

Correct selection + calm law application = guaranteed marks.

📘 Centre of Mass & System of Particles – Complete Physics Library

This library is a complete learning package for Intermediate + IIT JEE Physics covering Centre of Mass and System of Particles.

It includes theory, solved examples, objective questions, IIT-level problems, revision strategies, tricks, and exam-oriented guidance.

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📂 Stage 1: Intermediate Complete Notes (Concept Foundation)

1. Part 1
2. Part 2
3. Part 3
4. Part 4
5. Part 5
6. Part 6
7. Part 7
8. Part 8
9. Part 9
10. Part 10

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📂 Stage 2: Advanced Concepts & 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

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📂 Stage 3: Objective Questions, Tough Problems & Revision

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
40. Part 40
41. Part 41
42. Part 42
43. Part 43
44. Part 44
45. Part 45
46. Part 46
47. Part 47
48. Part 48
49. Part 49
50. Part 50
51. Part 51
52. Part 52
53. Part 53
54. Part 54
55. Part 55
56. Part 56
57. Part 57

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🔗 Learning Hub & Community

• 📚 Shaktimatha Learning Resource Hub
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Prepared by: Shaktimatha Learning 🌱
Vision: Concept clarity • Logical thinking • Exam excellence