��CH3 - E xercises 2. ( a) 24 km / h , 1 8.7 km...

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Exercises 2. (a) 24 km / h , 18.7 km / h ; (b) 1.75 h 4. (a) Δx = 720 m + 1920 m = 2640 km, so v =2640 m / 180 s = 14.7 m / s; (b) Δx = 720m – 1920m = –1200 m, so v = –6.67 m / s 24. (a) (20 m / s) / 5 s = +4 m / s 2 ; (b) 5 m / s 2 ; (c) 2 s 28. 27 m , 9 m / s 35. (b) 14.3 mph / s ; (c) 8.4 s ; (d) 13 s at 105 mph 36. (a) 5 s, 40 m ; (b) v A = 8 m / s, v B = 16 m / s 38. (a) 6.75 × 10 5 m / s 2 ; (b) 1.33 × 10 . 3 s 47. (a) From Eq. 3.10 : 32 = 48 + 8a, so a = –2 m / s 2 ; (b) v = 12 m / s –(2 m / s 2 ) (4 s) = –4 m / s. 50. (a) v 0 2 = 2gy leads to v 0 = 7.92 m / s ; (b) t = 2v 0 / g = 1.62 s Problems 3. x T = 38 + 20t and x C = 20t + t 2 = x T +11 m. Thus t =7 s and Δx T = 178 –38 = 140 m. 6. (a) Equate x T = 60 + 10t and x C = 30t –2.5 t 2 to find t is not a real number, thus there is no collision. (b) x T = 65 +10t, x C =15 +30t – 1 / 2 at 2 . Set x T = x C to find t is not a real number if a > 4.0 m/s 2 . 9. (a) 25 2 = 15 2 + 2a (100), so a = 2 m / s 2 . v 2 = 25 2 + 2a (100) = 1025, so v = 32 m / s (b) 32 = 25 + 2t, so t =3.5 s
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��CH3 - E xercises 2. ( a) 24 km / h , 1 8.7 km...

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