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Unformatted text preview: 1/6 Sept 10, 2007 _ rm #5  Key l TableGroupJ 13.81 The crossbar of the goalposts in American football is yc = 10 ft above the ground. To kick a ﬁeld goal, the
kicker must make the ball go between the two uprights supporting the crossbar, and the ball must be above the
crossbar when it does so. Suppose that the kicker attempts a 40yd field goal (xC = 120 ft) and kicks the ball with
initial velocity v0 = 70 the and angle 6'0 = 40°. By what vertical distance does the ball clear the crossbar? 13.93 When an airplane touches down at r I 0, a stationary wheel is subjected to a constant angular acceleration (1 =110 racifs2 until I = 1 s.
(a) What is the wheel’s angular velocity at r = 1 s?
(b) At I = 0, the angle 6 = 0. Determine 6 in radians and in revolutions at 2‘ = 1 s. 13.106 Suppose that you want to design a medical centrifuge to subject samples to normal accelerations of 1000 g’s.
(a) If the distance from the center of the centrifuge to the sample is 300 mm, What speed of rotation in rpm is necessary?
(b) If you want the centrifuge to reach its design rpm in 1 min, what constant angular acceleration is necessary‘.J 3~U£} m [um 13.115 At the instant shown, the magnitude of the airplane’s velocity is 130 mls, its tangential component of acceleration is a; = —4 111/52, and the rate of change of its path angle is d6/dr = 59’s.
(a) What are the airplane’s velocity and acceleration in terms of normal and tangential components? (b) What is the instantaneous radius of curvature of the airplane’s path?
4 x €126.55“ 5 WL Wt"
13.126 oordinates ofa point moving in the x—y plane are
x=20+4tzmandy=10—r3m.
What is the instantaneous radius of curvature of the path of the point at t = 3 s? F=‘~(L®+1Hl)?+ (03(3);
1‘}: —; Q82?) 1" +9st 3
a : f at #690. ’17:(24 r f 175721
the = 2%4 1153:4337:
’ {wt—“1%er M/QEQ
at: ‘5? —123
‘1 Z )9]? “1/ch "L 696,04” :3. m (Ammwe sum} m+/M%WP %';gff*3ﬁf
5:9?Ffa‘f'j “m.—
wEIJ :
dr ﬁW‘HMT
,l w:f¢77ﬁﬁn 5% ﬂy”?
gf': Ham
F F 13.133* A car travels at 100 kmfh on a straight road ofinereasing grade whose vertical proﬁle can be
approximated by the equation shown. When the car’s horizontal coordinate is x = 400 m, what are the tangential and normal components of the car’s acceleration?
it ...
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 Fall '08
 Biggers
 Statics, Velocity, 5%, ham, 1 min, 10 ft

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