A piece of metal is pressed against the rim of a 1.6kg, 19-cm-diameter grinding wheel that is turning at 2400 rev/min. The metal has a coeffiecient of friction of .85 with respect to the wheel. When the motor is cut off, with how much force must you press to stop the wheel in 20 sec.?(adsbygoogle = window.adsbygoogle || []).push({});

Not sure I did this right, here's what I did:

2400 rev/min = [tex] 80 \pi[/tex] rad/sec. = [tex] \omega_0 [/tex].

t=20, and [tex] \omega_f = \omega_0 + \alpha t [/tex]. After plugging everything in (w_f=0) I got [tex] \alpha = -40 \pi [/tex] rad/sec^2. Since [tex] a = r \alpha [/tex], I got a = [tex] -3.4 \pi [/tex] m/sec^2. Then somehow from there I jumped to an answer of [tex] 4.624 \pi [/tex] N. I don't think that's right.

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# Homework Help: Torque/angular acceleration

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