Lesson 7 – Momentum & Collisions

Phase 3 – Complete Exam Mastery
Page 17 – How to THINK, DECIDE & SCORE in IIT / JEE

This page is the final brain-training layer. Students who master this page stop making panic mistakes and start making rank-saving decisions.

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🔹 Part 1: The 5-Second Question Scan Rule

Before solving any question, pause for 5 seconds and ask:

✔ Is this collision / explosion / rebound?
✔ Any external force present?
✔ Can COM frame simplify?
✔ Energy usable or dangerous?

Result: Wrong approach is avoided before it begins.

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🔹 Part 2: Decision Tree Used by Toppers

No external force → Momentum must be conserved
e = 0 → Perfectly inelastic
e = 1 → Elastic collision
Explosion → COM unchanged
Bounce → Think e² immediately

Toppers decide in 10 seconds. Others calculate for 3 minutes and still fail.

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🔹 Part 3: When to Solve & When to Skip

✔ 2 options eliminated → attempt
✔ Multi-correct + confusion → skip
✔ Lengthy + unclear → mark & move on
✔ Calm confidence → attempt late

Golden Rule: Skipping is also a strategy.

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🔹 Part 4: Top 7 Examiner Traps (Must Remember)

✔ KE assumed conserved automatically ❌
✔ Direction ignored ❌
✔ Wall treated as internal ❌
✔ Explosion treated as collision ❌
✔ COM misunderstood ❌
✔ Height vs time confusion ❌
✔ Panic due to long question ❌

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🔹 Part 5: 1-Day Before Exam – What to Revise

✔ Momentum conservation cases
✔ Elastic collision standard formulas
✔ e² height relation
✔ COM motion principles
✔ 5–10 previous objective traps

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🧠 Final Exam-Hall Mindset

Calm > Speed
Thinking > Formula
Elimination > Calculation
Accuracy > Attempt count
Confidence > Fear

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✅ Phase 3 Completed

You have completed:
✔ All objective levels (1–8)
✔ Problem-tackling strategies (Tips 1 & 2)
✔ Exam-hall thinking & decision control
✔ Rank-protection mindset

👉 Next: FINAL REVISION – Part 1 (Formulas + Visual Memory)