Re: classical physics - rod anchored to ground, rotational inertia
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problem 2: 7 pennies (uniform, equal disks) are arranged in a hexagonal planar pattern. whats the moment of inertia around the axis perpendicular to the plane of the pennies, thru the center penny
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Ok, got this one. Moment of inertia of a disk =.5*M*R^2
Parallel Axis Theorem: I = Icm + m*r^2
Icm is moment of inertia about center of mass.
Then, I = .5*M*R^2 + 6*(.5*M*R^2 +M*r^2)
I = 7/2*M*R^2 + 6*M*r^2
plugging in r=2R
I = 7/2*M*R^2 + 24*M*R^2
I = 55/2*M*R^2
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