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JEE Main 202628 JanuaryMorning Shift
Exam
JEE Main
Year
2026
Date
28 January
Shift
Morning Shift
Subject
Physics
Chapter
Rotational Motion

JEE Main 2026 · 28 January · Morning Shift · Physics · Rotational Motion

A solid sphere of radius 10 cm is rotating about an axis which is...

A solid sphere of radius 10 cm is rotating about an axis which is at a distance 15 cm from its centre. The radius of gyration about this axis is n cm\sqrt{n} \mathrm{~cm}. The value of nn is

Correct answer

0

Step-by-step solution

Using the parallel axis theorem for radius of gyration:
k2=kcm2+d2k^2 = k_{cm}^2 + d^2 where kcmk_{cm} is the radius of gyration about the center of mass and dd is the distance from the center.
For a solid sphere:
Icenter=25MR2I_{center} = \frac{2}{5}MR^2, so kcm2=25R2k_{cm}^2 = \frac{2}{5}R^2
With R=10R = 10 cm and d=15d = 15 cm:
k2=25(10)2+(15)2=40+225=265k^2 = \frac{2}{5}(10)^2 + (15)^2 = 40 + 225 = 265
Since k=nk = \sqrt{n}, we have n=265n = 265.
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