please give me problems with the answer for (everyday force(overcoming firiction)?

please give me problem solving with the answer I really need as many as you can

Anonymous2011-03-18T18:07:47Z

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Friction force to applied to stop a disk.
The 3.0 kg, 20 cm diameter disk is spinning at 340 rpm. How much friction force must the brake apply to the rim to bring the disk to a halt in 2.5 s?

w = 340 . 2 . π / 60 = 35.6 rad/s

Angular deceleration = 35.6 / 2.5 = 14.24 rad/s/s

MI = 1/2 m . r^2 = 0.5 . 3 . 0.1^2 = 0.015 kgm^2

Torque = MI . ang accel = 0.015 . 14.24 = 0.214 Nm

Force = Torque / radius 0.214 / 0.1 = 2.14 N