CHAPTER 4.
-------------
3. 1160 N.
5. a) W = N = 196 N. b) on 20 kg, 294 N, on 10 kg, 98.0 N.
8. mass > 1.8 kg.
12. 3.78 m/s^2 up.
23. 1410 N.
25. a) 31 N, 63 N, b) 36 N, 73 N.

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29. a) 320 N, b) 1.47 m/s^2.
(extra digit in part b, because number starts with a "1".)
37. a) 0.98, b) 0.91
40. 39-degrees.
44. mu=1.42 (assuming most of the weight on the rear tires.)
    mu=2.8  (assuming weight evenly distributed on all tires.)
56. 1.09 kg.

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52. a) 2.6 m/s^2, b) 6.9 m/s.
65. 133 N.
75. 82 m/s.
77. 4-degrees.
79. 940 N at 79-degrees above horizontal.



CHAPTER 5. 
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2. 4.69 g.
5. 9.18 m/s^2 = 0.937 g.
11. 30.4 m/s, 0.403 rev/s.
18. mu=0.22, No outward force, only their own inertia.
    There is an inward (normal) force, which is responsible for
    their centripetal acceleration.
21. mu = f_s/N = 0.22
25. 3.5 kN, 0.50 kN.

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28. 1470 N.
34. a) 9.79 m/s^2, b) 4.35 m/s^2.
43. 6320 m/s.
46. 5070 s.
77. 5070 s.


CHAPTER 6.
--------------
3. a) 920 J, b) 5200 J.
8. a) 376 N, b) -1350 J, c) -4110 J, d) 5470 J, e) 0 J (KE=const.).
(using 3 digits, considering these as intermediate results and trying 
  to keep similar errors.)
18. -532 kJ.
22. 27 m/s or 97 km/h.
27. 82 J.
31. a) 920 kJ, b) 920 kJ, c) actual work is greater, body is inefficient.

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34. 60.2 m/s.
38. 199 m/s.
42. a) 104 N/m,  b) 22 m/s^2 up.
43. 26 m/s, 12 m/s, 20 m/s.
51. a) 0.25, b) 5.4 m/s, c) heat, sound.
55. 0.40
60. 66 kW.
62. b) 370 kWh, c) 1.35 GJ, d) $45.

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