Q. 67

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Found in: Page 333

### Physics for Scientists and Engineers: A Strategic Approach with Modern Physics

Book edition 4th
Author(s) Randall D. Knight
Pages 1240 pages
ISBN 9780133942651

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# A 30-cm-diameter, 1.2 kg solid turntable rotates on a 1.2-cm-diameter, 450 g shaft at a constant 33 rpm. When you hit the stop switch, a brake pad presses against the shaft and brings the turntable to a halt in 15 seconds. How much friction force does the brake pad apply to the shaft?

The friction force applied by the break pad is 0.52 N

See the step by step solution

## Step 1: Given information

Mass of the turntable = 12.kgMass of the shaft =450 gm = 0.45 kgThe diameter of the turntable = 30 cm =0.3 mradius = 0.15 mThe diameter of the shaft = 1.2 cm = 0.012 mSo radius of shaft =0.006mTime taken to stop = 15 sec

The initial angular speed of the turntable =33 rpm = 3.45 rad/s

Final speed =0

## Step2: Explanation

Moment of inertia of turn table ( consider disk) is

Substitute the values we get

Find the retardation using

Now find the frictional force by equating torque

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