10.20. Set Up: Let the direction of rotation of the flywheel be positive. where must be in radians. Solve: (a) gives (b) gives (c) 10.21. Set Up: with in The speed of the weight is Since and are constant, the tension in the rope equals the weight of the object. Solve: (a) (b) so (c) Reflect: The rate at which the weight gains gravitational potential energy, equals the power output of the motor, so which agrees with the result we calculated for part (c). 10.22. Set Up: For a solid uniform sphere rotating about a diameter, Table 9.2 gives Solve: 10.23. Set Up: For a slender rod with the axis at one end, (Table 9.2). The angular velocity is related to the period T by Solve: 10.24. Set Up: and Solve: (a) (i) counterclockwise (ii) (iii) clockwise (b) The answers are all the same as in (a). 10.25. Set Up: Solve: (a) so (b) Find gives counterclockwise Reflect: The angular momentum increases as the brick falls because of the external torque of the gravity force. L
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