Problem

9.67 A vinyl record that is initially turning at $33 \frac{1}{3} \mathrm{rpm}$ slows uniformly to a stop in a time of $15.0 \mathrm{~s}$. How many rotations are made by the record while stopping?

Answer

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Answer

\(\boxed{4.17}\) rotations

Steps

Step 1 :Convert initial angular velocity from rpm to rad/s: \(\omega_{i} = 33.33 \times \frac{2\pi}{60} = 3.49 \, rad/s\)

Step 2 :Calculate angular displacement: \(\theta = \frac{\omega_{i} + \omega_{f}}{2} \times t = \frac{3.49 + 0}{2} \times 15 = 26.18 \, rad\)

Step 3 :Find the number of rotations: \(n = \frac{\theta}{2\pi} = \frac{26.18}{2\pi} \approx 4.17\)

Step 4 :\(\boxed{4.17}\) rotations

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