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Nov19-04, 07:14 PM
So I'm doing an online homework problem:
A potter's wheel - a thick stone disk of radius 0.405 m and mass 112 kg - is freely rotating at 48.0 rev/min. The potter can stop the wheel in 5.67 s by pressing a wet rag against the rim and exerting a radially inward force of 69.1 N. Find the effective coefficient of kinetic friction between the wheel and rag.
Round your answer to three significant figures.
f = \frac {I \omega_i}{r(\Delta t)} = \frac {(112 kg) (0.405 m^2)(48.0 rev/min)} {(0.405 m)(5.67 s)} \left(\frac{2\pi rad}{1 rev}\right) \left( \frac {1 min}{60 s}\right) = 40.2 N
\mu_k = \frac {f}{n} = \frac {40.2}{69.1}=0.582
Trouble is, I keep getting "WRONG".
Am I doing it wrong? I also tried with different # of significant digits and nothin. Any help would be great.
A potter's wheel - a thick stone disk of radius 0.405 m and mass 112 kg - is freely rotating at 48.0 rev/min. The potter can stop the wheel in 5.67 s by pressing a wet rag against the rim and exerting a radially inward force of 69.1 N. Find the effective coefficient of kinetic friction between the wheel and rag.
Round your answer to three significant figures.
f = \frac {I \omega_i}{r(\Delta t)} = \frac {(112 kg) (0.405 m^2)(48.0 rev/min)} {(0.405 m)(5.67 s)} \left(\frac{2\pi rad}{1 rev}\right) \left( \frac {1 min}{60 s}\right) = 40.2 N
\mu_k = \frac {f}{n} = \frac {40.2}{69.1}=0.582
Trouble is, I keep getting "WRONG".
Am I doing it wrong? I also tried with different # of significant digits and nothin. Any help would be great.