Gravitation – Phase 3 Exam Mastery

Page 2 • 10 Deadly IIT/JEE Traps & Escape Techniques

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This page is designed to protect marks. Most students lose gravitation marks not due to weak theory, but due to examiner-designed traps.

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TRAP 1: Assuming Energy Conservation Everywhere

Mistake: Applying energy conservation even when non-conservative forces act.

Escape:

• Check for thrust, impulse, external work
• If sudden velocity change → energy NOT conserved

Exam Tip: Impulse problems → conserve momentum, not energy.

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TRAP 2: Forgetting Rotational Energy of Satellites

Mistake: Ignoring rotational kinetic energy when satellite spins.

Escape:

• Read question carefully
• If rotation mentioned → add (½Iω²)

IIT Favourite Trap

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TRAP 3: Wrong Reference Radius

Mistake: Using Earth’s radius instead of (R + h).

Escape:

• Always draw centre-to-particle distance
• Measure r from Earth’s centre

Golden Rule: Gravity works from centre, not surface.

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TRAP 4: Mixing g-Variation Formulae

Mistake: Using linear depth formula for height problems.

Escape:

• Depth → linear relation
• Height → inverse square relation

Memory Hook: Inside Earth → straight line Outside Earth → curve

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TRAP 5: Assuming Circular Orbit Automatically

Mistake: Treating all satellite motion as circular.

Escape:

• Check velocity magnitude & direction
• Any change → elliptical orbit

Key Insight: Circular orbit needs exact speed.

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TRAP 6: Ignoring Direction of Velocity Change

Mistake: Ignoring tangential vs radial impulse.

Escape:

• Tangential impulse → changes energy
• Radial impulse → changes shape of orbit

Advanced Concept: Direction matters more than magnitude.

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TRAP 7: Misunderstanding Escape Velocity

Mistake: Thinking escape velocity means object escapes immediately.

Escape:

• Escape velocity → zero speed at infinity
• Object still slows down gradually

Conceptual Question Favourite

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TRAP 8: Forgetting System Energy Reference

Mistake: Taking zero potential at wrong reference.

Escape:

• For gravity, zero at infinity (standard)
• Be consistent throughout solution

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TRAP 9: Over-Calculating Simple Problems

Mistake: Writing long derivations for direct formula questions.

Escape:

• Recall standard results
• Use proportional reasoning

Topper Habit: Minimum writing, maximum clarity.

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TRAP 10: Panic on Multi-Step Questions

Mistake: Seeing length and panicking.

Escape:

• Break question into parts
• Solve one physical idea at a time

Psychological Edge: Long question ≠ difficult question.

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FINAL EXAM SHIELD

If you avoid these 10 traps, your gravitation score automatically jumps.

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Phase 3 • Page 2 Completed Successfully ✅