Sit a full JEE Main paper, free
25 questions, 45 minutes, out of 100, marked the way the exam marks it. No payment, no card, and no account needed to start.
1,000 XP coins free the first time you open your portal — enough to open a whole chapter level there and then.
Gravitation is a chapter of a few formulas used over and over. JEE Main leans on three of them: how g changes with height and depth, escape and orbital speed, and the energy of a satellite. The sign of the potential energy is where most marks are lost — it is negative, and it stays negative, and that minus sign is doing real work in every energy question here. Ten questions below. Give them ten honest minutes.
What this chapter carries in JEE Main
- Usually 1 to 2 questions every year, which is 4 to 8 marks.
- Satellites, orbital energy and escape velocity are the regular ones.
- Variation of g and Kepler’s laws fill the rest.
What the syllabus says
In the syllabus (Unit 6, Gravitation): The universal law of gravitation, acceleration due to gravity and how it changes with altitude and depth, Kepler’s laws of planetary motion, gravitational potential energy and gravitational potential, escape velocity, motion of a satellite, orbital velocity, time period and energy of a satellite.
Taken out in 2024: geostationary satellites.
Taken from the NTA syllabus for JEE Main 2027. See the full syllabus, unit by unit.
Formulas you must know by heart
| Newton’s law of gravitation | F = Gm1m2/r2 |
| Acceleration due to gravity | g = GM/R2 |
| At a small height | g′ = g(1 − 2h/R) |
| At a depth | g′ = g(1 − d/R) |
| Gravitational potential energy | U = − GMm/r |
| Gravitational potential | V = − GM/r |
| Escape velocity | ve = √(2gR) = 11.2 km/s |
| Orbital velocity | vo = √(GM/r), and ve = √2 vo |
| Period of a satellite | T = 2π√(r3/GM) |
| Total energy in orbit | E = − GMm/2r |
| Kepler’s third law | T2 ∝ r3 |
Compare the two lines for height and depth. Going up, g falls twice as fast as it does going down. A body 1 km above the ground loses twice the g that a body 1 km below it does.
Ten questions. Give yourself ten minutes.
Write your answers down before you scroll. A question you looked up is a question you have not answered.
Q1. For a small height h above the earth’s surface, the acceleration due to gravity becomes
- (a) g(1 − h/R)
- (b) g(1 − 2h/R)
- (c) g(1 + 2h/R)
- (d) g(1 − h/2R)
Q2. At a depth d below the earth’s surface, the acceleration due to gravity becomes
- (a) g(1 − d/R)
- (b) g(1 − 2d/R)
- (c) g(1 + d/R)
- (d) g, unchanged
Q3. The escape velocity from the surface of the earth is about
- (a) 7.9 km/s
- (b) 11.2 km/s
- (c) 9.8 km/s
- (d) 22.4 km/s
Q4. For a satellite orbiting close to the earth, the ratio of the escape velocity to the orbital velocity is
- (a) 1
- (b) √2
- (c) 2
- (d) 1/√2
Q5. A planet orbits at four times the distance of another. Its period is larger by a factor of
- (a) 2
- (b) 4
- (c) 8
- (d) 16
Q6. The gravitational potential energy of two masses separated by r is
- (a) Gm1m2/r
- (b) −Gm1m2/r
- (c) −Gm1m2/r2
- (d) Gm1m2/r2
Q7. The escape speed from the surface of a planet does NOT depend on
- (a) the mass of the planet
- (b) the radius of the planet
- (c) the mass of the body being thrown
- (d) the value of G
Q8. The weight of a body placed at the centre of the earth is
- (a) a maximum
- (b) zero
- (c) the same as at the surface
- (d) infinite
Q9. The extra energy needed to make a satellite in an orbit of radius r escape altogether is
- (a) GMm/r
- (b) GMm/2r
- (c) 2GMm/r
- (d) GMm/4r
Q10. Kepler’s second law, that equal areas are swept in equal times, is a statement of the conservation of
- (a) energy
- (b) linear momentum
- (c) angular momentum
- (d) mass
Answer key, with a hint for each
| Q1 | (b) | Expand gR2/(R + h)2 by the binomial approximation and keep the first two terms. |
| Q2 | (a) | Only the sphere below you pulls, and its mass falls off faster than the distance does. |
| Q3 | (b) | ve = √(2gR) with g = 9.8 and R = 6400 km. |
| Q4 | (b) | ve = √2 vo, which is why 7.9 km/s becomes 11.2 km/s. |
| Q5 | (c) | T2 ∝ r3, so T goes as r3/2, and 43/2 = 8. |
| Q6 | (b) | Negative, because work has to be done to pull the two masses apart to infinity. |
| Q7 | (c) | vₑ = √(2GM/R). The mass of the escaping body cancels out of the energy equation, so a stone and a satellite need exactly the same escape speed from the same planet. |
| Q8 | (b) | There is no mass below it in any direction, so the pulls from every side cancel exactly. |
| Q9 | (b) | The total energy in orbit is −GMm/2r, and escape means reaching zero. |
| Q10 | (c) | The areal velocity stays constant precisely because the gravitational force is central and exerts no torque. |
Now mark yourself honestly
JEE Main marks the way it marks. Use the same rule here:
- +4 for a right answer
- −1 for a wrong one
- 0 for a blank
So ten questions here are out of 40. In the real paper, 25 Physics questions are out of 100.
If you scored 32 or more, the basics of this chapter are secure. Move to harder questions, not more of these.
If you scored below 24, do not feel bad about it. You have just found out something useful before the exam did. Go back to the formula table above, learn it properly, and sit these ten again tomorrow.
And if you guessed a few and they landed, count those as wrong. A guess that works once will not work in January.
The full chapter, on a clock
Ten questions tell you a little. Twenty-five tell you the truth.
The Foundation paper for Gravitation is waiting for you on the portal: 25 questions, 45 minutes, marked out of 100, with the answer key and a hint for every question. Sit it tonight and you will know exactly where this chapter stands.
Free the moment you register
1,000 XP coins, free
A Foundation paper opens for 230 coins, so your first four are already paid for. And every paper you sit sincerely pays you more.
Every chapter of JEE Main Physics has three papers on the portal: Foundation, Intermediate and Expert. You move up only when you clear the one below. 30 chapters, 90 papers, open 24×7.
Want to know how many marks this chapter usually carries? See the JEE Main Physics chapter-wise weightage.
All the formulas for every chapter in one place: JEE Main Physics formula sheet.
One JEE Main Physics question every morning
It comes at 7 AM on Telegram. Tap the option you think is right and you will know at once whether it was. The worked hint follows the next morning.