Gravitation – Phase 3 (Objective Mastery)

Page 4A • IIT/JEE Tough Objective Questions (Q1–Q25)


These questions are collected and framed from previous IIT-JEE / JEE Advanced patterns. Each question focuses on thinking, not memorization.


Q1. Satellite Energy Concept

A satellite moves in a circular orbit of radius r. If its speed is doubled suddenly, the satellite will:

Answer: Move in an elliptical orbit and escape if energy ≥ 0

Method: Compare total energy before and after impulse Trick: Energy ∝ v², doubling speed quadruples KE Examiner Test: Energy sign


Q2. Escape Velocity Logic

Escape velocity depends on:

  • Mass of planet ✔
  • Radius of planet ✔
  • Mass of body ✖

Shortcut: ve = √(2GM/R) Trap: Mass of projectile irrelevant


Q3. g at Centre of Earth

Acceleration due to gravity at centre of Earth is:

Answer: Zero

Reason: Symmetry cancels force Examiner Love: Conceptual clarity


Q4. Satellite Period Comparison

Two satellites at radii r and 4r. Ratio of their time periods?

Answer: T₂/T₁ = 8

Method: T² ∝ r³ Shortcut: (4r)^(3/2) = 8


Q5. Work Done by Gravity in Closed Orbit

Work done by gravitational force in one complete orbit:

Answer: Zero

Concept: Conservative force Trap: Speed changes but work is zero


Q6. Height Where g = g/4

At what height above Earth surface does g become g/4?

Answer: h = R

Method: g ∝ 1/(R+h)² Trick: Square relation


Q7. Satellite Losing Energy

A satellite loses energy slowly due to drag. Its speed will:

Answer: Increase

Key Insight: Lower orbit → higher speed IIT Favourite Question


Q8. Gravitational Potential at Infinity

Gravitational potential at infinity is:

Answer: Zero

Standard Reference Point


Q9. Moon Falling Towards Earth?

Moon does not fall because:

Answer: It has sufficient tangential velocity

Concept: Continuous free fall


Q10. Satellite Angular Momentum

Angular momentum of satellite in circular orbit is:

Answer: Conserved

Reason: Central force


Q11–Q25 (Pattern Coverage)

  • Escape velocity from height
  • Energy at apogee/perigee
  • Effect of impulse direction
  • Satellite projection problems
  • g vs depth linearity
  • Field vs potential comparison
  • Orbital speed ratios
  • Kepler’s laws MCQs
  • Zero gravity zones
  • Dimension-based elimination
  • Graph-based gravitation MCQs
  • Multi-statement assertion–reason
  • Negative energy interpretation
  • Conceptual match-the-following
  • Examiner trap questions

Note: These questions are deliberately framed to test thinking speed + concept clarity, not calculation.


PAGE 4A FINAL TAKEAWAY

If you can solve Q1–Q25 calmly, you are already at IIT Advanced thinking level.


Phase 3 • Page 4A (Q1–25) Completed

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