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Unformatted text preview: Chapter 10 10.9 A disk, initially rotating at 120 rad/s is slowed down with a constant angular acceleration of magnitude of 4.0 rad / s 2 (a) How much time does the disk take to stop? (b) Through what angle does the disk rotate during that time? i = f = ? i = 120 rad / s f = = 4 rad / s 2 t = ? f = i + t t = f i = rad / s 120 rad / s 4.0 rad / s 2 = 30 s f = i + i t + 1 2 t 2 f = + 120 rad / s 30 s + 1 2 4 rad / s 2 (30 s ) 2 = 1800 rad 10.12 Starting from rest, a disk rotates about its central axis with constant angular acceleration. In 5.0 s, it rotates 25 rad. During that time, what are the magnitudes of (a) the angular acceleration and (b) the average angular velocity? (c) What is the instantaneous angular velocity of the disk at the end of the 5.0 s? (d) With the angular acceleration unchanged, through what additional angle will the disk turn during the next 5s. This problem is the angular analog of many of the constant linear acceleration problems that we did. Parts (a) and (b) ... the angular acceleration and average angular velocity....
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 Spring '10
 jojo

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