Sign in
12thPass logo
New chatPYQ LibraryDoubtsRank report
Sign in to see Recents

Your guest activity stays on this device

Sign in to save progress →
Sign in

Gravitation question

2024 · 31 Jan · Shift 2 · Q79
Guest · filters and generic practice availableBrowsing as a guest · PYQ filters and generic practice are available. Sign in only for personalised features and saved progress.
  1. PYQ Library
  2. /JEE Main
  3. /Physics
  4. /Gravitation
  5. /2024 · 31 Jan · Shift 2 · Q79

Gravitation question

2024 · 31 Jan · Shift 2 · Q79

JEE MainPhysicsGravitationMCQ+4 / −1
The mass of the moon is 1144\frac{1}{144}1441​ times the mass of a planet and its diameter is 116\frac{1}{16}161​ times the diameter of a planet. If the escape velocity on the planet is vvv, the escape velocity on the moon will be :
  1. A
    v4\frac{\mathrm{v}}{4}4v​
  2. B
    v6\frac{\mathrm{v}}{6}6v​
  3. C
    V12\frac{\mathrm{V}}{12}12V​
  4. D
    v3\frac{\mathrm{v}}{3}3v​
View written solutionFree

Correct answer: D

  1. Use the formula for escape velocity

The escape velocity from the surface of a body is

ve=2GMRv_e = \sqrt{\frac{2GM}{R}}ve​=R2GM​​

So,

ve∝MRv_e \propto \sqrt{\frac{M}{R}}ve​∝RM​​

where MMM is the mass and RRR is the radius of the body.


  1. Relate moon's mass and radius to the planet

Let the planet have mass MMM and radius RRR.

Given:

  • Mass of moon =1144M= \frac{1}{144}M=1441​M
  • Diameter of moon =116= \frac{1}{16}=161​ times diameter of planet

Since radius is proportional to diameter,

Rm=116RR_m = \frac{1}{16}RRm​=161​R


  1. Write escape velocity ratio

If escape velocity on the planet is vvv, then

v=2GMRv = \sqrt{\frac{2GM}{R}}v=R2GM​​

For the moon,

vm=2G(M/144)R/16v_m = \sqrt{\frac{2G(M/144)}{R/16}}vm​=R/162G(M/144)​​

Simplify:

vm=2GMR⋅16144v_m = \sqrt{\frac{2GM}{R} \cdot \frac{16}{144}}vm​=R2GM​⋅14416​​

vm=2GMR⋅19v_m = \sqrt{\frac{2GM}{R} \cdot \frac{1}{9}}vm​=R2GM​⋅91​​

vm=132GMRv_m = \frac{1}{3}\sqrt{\frac{2GM}{R}}vm​=31​R2GM​​

vm=v3v_m = \frac{v}{3}vm​=3v​


  1. Check options
  • A: v4\frac{v}{4}4v​ ❌
  • B: v6\frac{v}{6}6v​ ❌
  • C: v12\frac{v}{12}12v​ ❌
  • D: v3\frac{v}{3}3v​ ✅

So the correct answer is:

v3\boxed{\frac{v}{3}}3v​​

PreviousNext

More from Gravitation

  • If earth has a mass nine times and radius twice to that of a planet P. Then 3ve​​x​ ms−1 will be the minimum velocity required by a rocket to pull out of gravitational force of P, where ve​ is…2023 · MCQ
  • Given below are two statements: Statement I: Acceleration due to gravity is different at different places on the surface of earth. Statement II: Acceleration due to gravity increases as we go down below the earth's surface. In the light of…2023 · MCQ
  • The escape velocities of two planets A and B are in the ratio 1:2. If the ratio of their radii respectively is 1:3, then the ratio of acceleration due to gravity of planet A to the acceleration of gravity of…2023 · MCQ
  • For a body projected at an angle with the horizontal from the ground, choose the correct statement.2023 · MCQ
  • Given below are two statements : one is labelled as Assertion A and the other is labelled as Reason R. Assertion A : Earth has atmosphere whereas moon doesn't have any atmosphere. Reason R : The escape velocity on…2023 · MCQ
  • A planet has double the mass of the earth. Its average density is equal to that of the earth. An object weighing W on earth will weigh on that planet:2023 · MCQ
  • The weight of a body on the surface of the earth is 100 N. The gravitational force on it when taken at a height, from the surface of earth, equal to one-fourth the radius of the earth is:2023 · MCQ
  • Choose the incorrect statement from the following:2023 · MCQ