Page 141 - Schaum's Outline of Theory and Problems of Applied Physics

126 ROTATIONAL MOTION [CHAP. 10

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10.24. A wheel whose moment of inertia is 0.4 slug·ft is rotating at 1500 rev/min. (a) What constant torque is required
to increase its angular velocity to 2000 rev/min in 8s? (b) How many turns does the wheel make while it is being
accelerated? (c) How much work is done on the wheel?
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10.25. A disk whose moment of inertia is 1 kg·m is rotating at 100 rad/s. This disk is pressed against a similar disk that is
able to rotate freely but is initially at rest. The two disks stick together and rotate as a unit. (a) Find the final angular
velocity of the combination. (b) How much energy was lost to friction when the disks were brought together?

Answers to Multiple-Choice Questions

10.1. (c) 10.10. (b)

10.2. (d) 10.11. (b)

10.3. (a) 10.12. (c)
10.4. (c) 10.13. (a)

10.5. (b) 10.14. (c)

10.6. (a) 10.15. (c)

10.7. (b) 10.16. (d)
10.8. (d) 10.17. (b)

10.9. (b) 10.18. (c)

Answers to Supplementary Problems

10.1. Ball A reaches the bottom first because all of its initial PE becomes KE of linear motion. Part of ball B’s initial PE
becomes KE of rotation, so there is less PE available to become KE of linear motion. As a result, B moves more
slowly downward than A.

10.2. They will reach the bottom at the same time.
10.3. The rectangle.

10.4. (a) 78.5 rad (b) 0.032 rev (c) 1.5 rev

10.5. (a) 0.558 rad (b) 275 ◦ (c) 22.5 ◦
10.6. 105 cm

10.7. (a) 42 rad/s (b) 0.875 ft/s

10.8. 238 rev/min

10.9. 11.1 rad/s