A device for measuring the moment of inertia of an object is shown in Figure. A circular platform has a concentric drum of radius 10 cm about which a string is wound. The string passes over a frictionless pulley to a weight of mass M. The weight is released from rest, and the time for it to drop a distance D is measured. The system is then re wound, the object placed on the platform, and the system again released from rest. The time required for the weight to drop the same distance D then provides the data needed to calculate I. With M = 2.5 kg, and D = 1.8 m, the time is 4.2s.

(a) Find the combined moment of inertia of the platform, drum, shaft, and pulley.

(b) With the object placed on the platform, the time is 6.8 s for D = 1.8 m. Find I of that object about the axis of theplatform.

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