Two circular discs of same mass and radius are shaped like a convex and concave lens respectively. If both are rotated about an axis perpendicular to their planes and passing through their centres, which one will have a greater moment of inertia? Give reason.

Asked by pshiveshwar | 15th Mar, 2019, 09:55: PM

Expert Answer:

Moment of inertia of the disc which is having the shape of concave lens is greater than that of the disc of convex shaped.
Most of the mass is concentrated near axis of rotation for convex shaped disc, whereas concave shape disc have more mass
away from axis of rotation. Hence radius of gyration of concave shape disc is greater than the radius of gyration of convex shape.
Since each disc is having same mass but radius of gyration of concave shape disc is greater, moment of inertia of
concavs shape disc is greater than the moment of inertia of convex shape disc

Answered by Thiyagarajan K | 15th Mar, 2019, 10:51: PM

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