Lesson 7 – Momentum & Collisions

Phase 3: Exam Mastery
Page 16 – Objective 9: How to Tackle Problems (Tips–2)

This page focuses on how to reduce time, avoid traps, and increase accuracy while solving momentum and collision problems in IIT-JEE & Board exams.

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🔹 Tip 6: Use Option Elimination (Not Full Solution)

In objective questions, full calculation is rarely required. Learn to eliminate wrong options logically.

✔ Check units first
✔ Check extreme cases (m ≫ M or e = 0)
✔ Check sign (positive/negative velocity)

Example: If answer has velocity greater than initial in inelastic collision → wrong.

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🔹 Tip 7: Memorize High-Return Standard Results

Some results appear again and again in exams. Memorizing them saves precious time.

✔ Elastic collision (equal masses) → exchange velocities
✔ e = 0 → bodies stick together
✔ Height after bounce = e²h
✔ COM velocity = constant (no external force)

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🔹 Tip 8: Approximation & Physical Sense

IIT questions often expect physical judgment, not exact arithmetic.

✔ Heavier mass → smaller velocity change
✔ Perfectly elastic → no KE loss
✔ Perfectly inelastic → maximum KE loss

If your answer violates physical sense, recheck immediately.

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🔹 Tip 9: Handle Lengthy Questions Calmly

Lengthy questions are designed to create panic. Calm students score here.

✔ Break question into stages
✔ Solve collision part first
✔ Ignore unnecessary data

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🔹 Tip 10: Negative Marking Protection

Protect your score by avoiding blind attempts.

✔ If 2 options eliminated → attempt
✔ If confusion between 3 → skip
✔ Never guess multi-correct blindly

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🧠 Objective–9 (Tips–2) Final Summary

✔ Eliminate before calculating
✔ Memorize standard collision results
✔ Trust physical intuition
✔ Calm reading beats fast math
✔ Marks saved = rank improved

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📌 Next

Next page will include:
✔ Ultimate exam-day checklist
✔ 7-day & 1-day revision plan
✔ How toppers revise this chapter

👉 Next: Objective 10 – Final Exam-Day Strategy