Chapter 17
284
17.1 FD = CD2
1
2
A: A = D L = (0.025 m)(1 m) = 0.025 m2
a. Water at 15 C: = 1000 kg/m3;
= 1.15 106 m2/s
b. Air at 10 C: = 1.247 kg/m3;
= 1.42 105 m2/s
FD = (1.30)(0.5)(1.247 kg/m2)(0.15 m/s)2(0.025 m2) = 4.56 104 N
17.2 Assume a smooth sphere
a. 3
15 km 10 m 1 h
2 2
2
(2.0) 3.142 m
D
Similarly for (b), (c), and (d):
(km/h)
(m/s) NR CD FD(N)
(a) 15 4.17 6.27 105 0.20 7.06
CHAPTER SEVENTEEN
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DRAG AND LIFT
289
a
.
Square c
y
li
n
d
e
r
:
L
= 9
in
1
ft
/12
i
n = 0
.
75
f
t
b. Assume CD = 1.60 Square cylinder Point first orientation
c. Circular cylinder: D = 9.0 in = 0.75 ft
d. Elliptical cylinder: L = 18 in = 1.50 ft; h = 9.00 in = 0.75 ft; L/h = 2.0
17.17 FD = CD2
1
2
A
:
= 65 mi 5280 ft 1 h
h mi 3600 s = 95.3 ft/s
17.18 tot disks tubes
=
D D D
F F F:
= 100 mi/hr = 147 ft/s (See Prob. 17.16):
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291
