479 Horizontal Motion: The horizontal component of velocity ... - Wuala

91962_05_R1_p0479-0512 6/5/09 3:53 PM Page 493
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R1–19. At the instant shown, cars A and B travel at speeds
of 55 mi>h and 40 mi>h, respectively. If B is decreasing its
speed at 1500 mi>h 2 while A is increasing its speed at
800 mi>h 2 , determine the acceleration of B with respect to
A. Car B moves along a curve having a radius of curvature
of 0.75 mi.
v B 40 mi/h
B
A 30
v A 55 mi/h
(a B ) n = v2 B
r = (40)2
0.75
= 2133.33 mi>h2
a B = a A + a B>A
2133.33 sin 30°i + 2133.33 cos 30°j + 1500 cos 30°i - 1500 sin 30°j
= -800i + (a B>A ) x i + (a B>A ) y j
( : + ) 2133.33 sin 30° + 1500 cos 30° = -800 + (a B>A ) x
(a B>A ) x = 3165.705 :
( + c) 2133.33 cos 30° - 1500 sin 30° = (a B>A ) y
(a B>A ) y = 1097.521 c
(a B>A ) = 2(1097.521) 2 + (3165.705) 2
a B>A = 3351 mi>h 2 = 3.35 A10 3 B mi>h 2
u = tan -1 a 1097.521
3165.705 b = 19.1° a
Ans.
Ans.
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