Question

Two discs of the same material & thickness have radii 0.2 m and 0.6 m. Their moments of inertia about their axes will be in the ratio:

• A. 1 : 81
• B. 1 : 27
• C. 1 : 9
• D. 1 : 3.

Answer 1

Answer: (A)

1 : 81

Answer 2

⇒

(As t and $\rho$are same)

∴$\frac { I _ { 1 } } { I _ { 2 } } = \left( \frac { R _ { 1 } } { R _ { 2 } } \right) ^ { 4 } = \left( \frac { 0.2 } { 0.6 } \right) ^ { 4 } = \frac { 1 } { 81 }$