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Unformatted text preview: CIRCULAR MOTION AND GRAVITATION 6
11. B 12. C 13. A 14. A 15. C Answers to Multiple-Choice Problems
1. D 2. B 3. C 4. A 5. C 6. C 7. C 8. A 9. D 10. B Solutions to Problems
6.1. Set Up: The path shows the relative size of the radius of curvature R of each part of the track. RB . RC. A straight line is an arc of a circle of inﬁnite radius, so RA S ` . v2 S Solve: arad 5 . At A, arad 5 0. arad, B , arad, C. In each case, a rad is directed toward the center of the circular path. R S The net force is proportional to a rad and is shown in Figure 6.1. B Fnet, B Fnet, A 5 0 A Fnet, C C Figure 6.1 Reﬂect: The road must exert a greater friction force on the car when it makes tighter turns that have smaller radii of curvature. 6.2. Set Up: Since the stone travels in a circular path, its acceleration is arad 5 v2 / R, directed toward the center of the
circle. The only horizontal force on the stone is the tension of the string. Set the tension in the string equal to its maximum value. Solve: (a) The free-body diagram for the stone is given in Figure 6.2. In the diagram the stone is at a point to the right of the center of the path. 6-1 ...
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