The figure shows two solid discs with radius R and r respectively. If mass per unit area is same for both, what is the ratio of MI of bigger disc around axis AB (which is &perp; to the plane of the disc and passing through its centre) to MI of smaller disc around one of its diameters lying on its plane? Given 'M' is the mass of the larger disc. (MI stands for moment of inertia)

2R⁴ : r⁴

R² : r²

2r⁴ : R⁴

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Moment of Inertia Physics System of Particles and Rotational Motion Physics Class 11th

The figure shows two solid discs with radius R and r respectively. If mass per unit area is same for both, what is the ratio of MI of bigger disc around axis AB (which is ⊥ to the plane of the disc and passing through its centre) to MI of smaller disc around one of its diameters lying on its plane? Given 'M' is the mass of the larger disc. (MI stands for moment of inertia)

Option 1 -

R² : r²

Option 2 -

2r⁴ : R⁴

Option 3 -

2R⁴ : r⁴

Option 4 -

2R² : r²

2 Views | Posted a month ago

Asked by Shiksha User

1 Answer

Answered by

Vishal Baghel | Contributor-Level 10

a month ago

Correct Option - 3

Detailed Solution:

I? / I? = (MR²/2) / (mr²/4)
[ M = σπR², m = σπr² ]
= 2 (M/m) (R²/r²)
= 2 (σπR²/σπr²) (R²/r²)
= 2 (R²/r²)² = 2R? /r?

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