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kirby27
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Two unequal masses m and 2m are attached to a thin bar of negligible mass that rotates about an axis perpendicular to the bar. When m is a distance 2d from the axis and 2m is a distance d from the axis, the moment of inertia of this combination is I. If the masses are now interchanged, the moment of inertia will be?
This is the work I tried:
The mases are m and 2m
The distance of the mass m from the axis is 2d
The distance of the mass 2m from the axis is d
The moment of inertia of the masse before exchanged is
I = m(2d)^2 + 2m(d)^2
I = 6md^2
The moment of inertia of the masse After exchanged is
The distance of the mass m from the axis is d
The distance of the mass 2m from the axis is 2d
I = m(d)^2 + 2m(2d)^2
I = 8md^2
I thought that after the masses were interchanged, the I would be 2I, the difference between before and after. The answer was wrong. I think the answer might be (2/3)I but I'm not sure. help is much appreciated
This is the work I tried:
The mases are m and 2m
The distance of the mass m from the axis is 2d
The distance of the mass 2m from the axis is d
The moment of inertia of the masse before exchanged is
I = m(2d)^2 + 2m(d)^2
I = 6md^2
The moment of inertia of the masse After exchanged is
The distance of the mass m from the axis is d
The distance of the mass 2m from the axis is 2d
I = m(d)^2 + 2m(2d)^2
I = 8md^2
I thought that after the masses were interchanged, the I would be 2I, the difference between before and after. The answer was wrong. I think the answer might be (2/3)I but I'm not sure. help is much appreciated
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