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## Homework Statement

The shows an arrangement of 15 identical disks that have been glued together in a rod-like shape of length

*L =*1.0000 m and (total) mass

*M =*100.0 mg. The disks are uniform, and the disk arrangement can rotate about a perpendicular axis through its central disk at point O. (a) What is the rotational inertia of the arrangement about that axis? (b) If we approximated the arrangement as being a uniform rod of mass M and length L, what percentage error would we make in calculating the rotational inertia?

*M =*100.0 mg = 1×10

^{-4}kg

*L =*1.0000 m

*# of disks =*15

## Homework Equations

Inertia of a disk about a central diameter

*I = (MR*

^{2})/2Inertia of set of particles

*I = ∑m*

_{i}r_{i}^{2}## The Attempt at a Solution

*I*

_{total}=*(MR*^{2})/4 +*∑m*

_{i}r_{i}^{2}*I*

_{total}= ML^{2}/ 4⋅30^{2}+ (2M/15)(1 + 4 + 9 + 16 + 25 + 36 + 49)(L/15)*I*_{total}= 8.298 kg - m^{2}Did I have the right solution?

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