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duplaimp
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Homework Statement
A dumbbell has two spheres of radius 0.10m and mass 10kg (each). The two spheres are connected using a bar with length 1.0m and mass 12kg.
What is the moment of inertia of the dumbbell about an axis perpendicular to an axis at the bar's center of mass?
Moment of inertia of a sphere through its center of mass: [itex]\frac{2}{5}MR^{2}[/itex]
Moment of inertia of a bar through its center of mass: [itex]\frac{2}{12}ML^{2}[/itex]
The Attempt at a Solution
I tried the following:
(sphere) [itex]Ip = Icm + Md^{2}[/itex] <=> Ip = [itex]\frac{2}{5} MR^{2} + M(\frac{L}{2} + R)^2[/itex] <=> Ip = [itex]\frac{7}{5} M R^{2} + M\frac{L^{2}}{4}[/itex]
(bar) I = [itex]\frac{2}{12} ML^{2}[/itex]
Then I multiplied Ip by 2 and sum I (of the bar). Itotal = 2Ip + I
But the value I am getting is wrong. What I am doing wrong?
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