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An old GRE problem asks what the moment of inertia of seven pennies, arranged in a hexagon with one in the center, all touching each others' edges is, about the axis that passes through the center of the central penny and is normal to the plane of the pennies.

Each penny is a uniform disc of mass m and radius r, and the answer is apparently 55mr/2.

Can anyone help with this?

Thanks

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# Homework Help: Moment of Inertia of a grouping of pennies

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