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Consider a prototype weed wacker, consisting of a thin inflexible string attached to a motor at its end. The string rotates around its end. The string has length L = 0.20 m and mass M = 0.015 kg.
What (constant) torque must the motor exert on the string
in order to bring it from rest to full speed in time t = 0.50 s? ”Full speed” is 1200 rpm. Neglect wind resistance. The moment of inertia for motion of
a rod about the end is I rod,end = 1/3ML 2
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