Question

120. A grindstone with a mass of 50 kg and radius 0.8 m maintains a constant rotation rate of 4.0 rev/s by a

motor while a knife is pressed against the edge with a force of 5.0 N. The coefficient of kinetic friction between

the grindstone and the blade is 0.8. What is the power provided by the motor to keep the grindstone at the

constant rotation rate?

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