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# Apply 'net torque = I alpha'; angular momentum for ratio of angular to initial velocity

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PART a. A small mass m is attached to one end of a rod of negligible mass. The other end of the rod is fixed so that the mass can move in a circle of radius R. A force F is applied tangent to the circle, giving the mass angular acceleration 'alpha'.
SEE ATTACHMENT #1 for a diagram showing parameters.
Apply 'net torque= I alpha' to express the torque in terms of the moment of inertia and the angular velocity.

PART b. Example: A uniform thin ring, mass M, radius R, is rotating about an axis at its center with initial angular velocity. At some instant it breaks and rearranges into a straight bar rotating about its center with final angular velocity. Apply conservation of angular momentum to find the ratio of final angular velocity to initial angular velocity.

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