Gravitation – Final Revision & Methods

One-Page Thinking System for Boards • JEE Main • JEE Advanced


This page is designed for last-stage preparation. If you revise only this before exam, you will:

  • Recall correct formulas instantly
  • Avoid examiner traps
  • Choose the fastest solving method
  • Stay calm inside the exam hall

METHOD 1: Identify the PROBLEM TYPE (5 seconds)

  • Falling body → Force + acceleration
  • Orbit → Centripetal + energy
  • Height / depth → g-variation
  • Escape → Total energy = 0

Rule: Wrong method = long solution = wrong answer.


METHOD 2: Formula FIRST, Numbers LATER

Never substitute values immediately.

  • Write symbolic equation
  • Simplify ratio / power
  • Then substitute

This avoids silly mistakes


METHOD 3: 5 MOST POWERFUL FORMULAS

  • v = √(GM/r)
  • E = −GMm / (2r)
  • ve = √(2GM/r)
  • T² ∝ r³
  • g ∝ 1/r²

90% problems solved here


METHOD 4: ENERGY SIGN CHECK

  • E < 0 → Bound orbit
  • E = 0 → Just escape
  • E > 0 → Hyperbolic path

Shortcut: Don’t solve fully — check sign.


METHOD 5: DIRECTION OF VELOCITY CHANGE

  • Tangential push → energy change
  • Radial push → orbit shape change
  • No push → same orbit

IIT favourite logic test


METHOD 6: g-VARIATION MEMORY MAP

  • Inside Earth → g ∝ r
  • Surface → maximum
  • Outside → g ∝ 1/r²

Graph questions solved instantly


METHOD 7: FIELD vs POTENTIAL RULE

  • Field → vector (can cancel)
  • Potential → scalar (adds)
  • Field = − gradient of potential

Classic examiner trap


METHOD 8: LIMITING CASE CHECK

Before final answer, ask:

  • What if r → ∞?
  • What if h = 0?
  • What if speed = orbital?

1 check = 4 marks saved


EXAM-HALL STRATEGY (VERY IMPORTANT)

  • Do gravitation first (easy marks)
  • Skip long numericals initially
  • Use elimination for MCQs
  • Never panic on length
  • Recheck units & powers

Gravitation is a scoring chapter


FINAL REVISION MANTRA

Think → Choose → Solve → Check
Not
Read → Panic → Calculate


Gravitation – Revision Completed Successfully

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