JEE Main 2020 — Gravitation Question with Solution
From: JEE Main 2020 (Online) 2nd September Morning Slot
Question
The mass density of a spherical galaxy varies
as
over a large distance ‘r’ from its centre.
In that region, a small star is in a circular orbit
of radius R. Then the period of revolution, T
depends on R as :
Choose an option
Show full solutionCorrect option: A
Correct answer
AT2 R
Step-by-step explanation
dm = dv
dm = (4r2dr)
dm = 4krdr
M = =
M =
M = 2kR2
For circular motion gravitational force will provide required centripetal force.
=
=
v =
Time period, T =
=
T2 R
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