Compact Disc.? A compact disc (CD) stores music in a coded pattern of tiny pits 10-7 m deep. The pits are arranged in a track that spirals outward toward the rim of the disc; the inner and outer radii of this spiral are 25.0 mm and 58.0 mm, respectively. As the disc spins inside a CD player, the track is scanned at a constant ?linear? speed of 1.25 m/s. (a) What is the angular speed of the CD when the innermost part of the track is scanned? The outermost part of the track? (b) The maximum playing time of a CD is 74.0 min. What would be the length of the track on such a maximum-duration CD if it were stretched out in a straight line? (c) What is the average angular acceleration of a maximum- duration CD during its 74.0-min playing time? Take the direction of rotation of the disc to be positive.

Solution 20E To solve this question, we shall have to consider the relationship between linear speed and angular speed. The relationship is given by v = r , where v is the linear speed, ris the radius of circular path and is the angular speed. (a) Given, linear speed v = 1.25 m/s 3 Inner radius of the spiral r 1 25.0 mm = 25.0 × 10 m The angular speed when the innermost part is scanned is, = v = 1.25 m/s = 50 rad/s i r1 25.0×103m Outer radius of the spiral r =258.0 mm = 58.0 × 10 3 m The angular speed when the outermost...