JEE Main 2017PhysicsGravitationHardMCQ

JEE Main 2017 — Gravitation Question with Solution

JEE Main 2017 (09 Apr Online)

Question

The mass density of a spherical body is given by ρr=kr for r≤R and ρr=0 for r>R, where r is the distance from the center. The correct graph that describes qualitatively the acceleration, a of a test particle as a function of r is:

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Show full solutionCorrect option: A
Correct answer
A

Step-by-step explanation



 For Inside point r≤R

g=E=Gr2∫0r4πr2drKr=GKr2×4πr22=2πGK=constant

For outside point r>R

E=gE=GMr2E=Gr2∫0R(4πr2dr')(Kr')E=4πKGr2[r'22]0R

E=2πKGr2R2

E∝1r2.

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About this question

This is a previous-year question from JEE Main 2017, covering the Gravitation chapter of Physics. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.