Official© Solutions Manual to Accompany Engineering Mechanics Statics,Pytel,4e

Chapter 1
1.1




1.2

W = gV = (7850)(9:81) (0:042 )(0:110) = 42:58 N
0:2248 lb
W = 42:58 N = 9:57 lb J
1:0 N

1.3
4:448 N 0:3048 m
(a) 400 lb ft = 400 lb ft = 542 N m J
1:0 lb 1:0 ft

6m 0:3048 ft 1:0 mi 3600 s
(b) 6 m/s = = 1: 247 mi/h J
s 1:0 m 5280 ft 1:0 h

20 lb 4:448 N 1:0 in.2
(c) 20 lb/in.2 = = 1: 379 105 N/m2
in.2 1:0 lb 645:2 10 6 m2
= 137:9 kPa J

500 slug 14:593 kg 39:37 in.
(d) 500 slug/in. = = 2: 87 105 kg/m J
in. 1:0 slug 1:0 m

1.4

30 mi 5280 ft 0:3048 m 1:0 gal
30 mi/gal =
gal 1:0 mi 1:0 ft 3:785 L
= 12 760 m/L = 12:76 km/L J

1.5
1 m 2 kg m2 kg m
(a) E = (1000 kg) 6 = 18 000 = 18 000 (m)
2 s s2 s2
= 18 000 N m = 18 kN m J

0:2248 lb 3:281 ft
(b) E = 18 000 N m = 18 000 N m
1:0 N 1:0 m
= 13 280 lb ft J




1
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, 1.6




1.7




1.8
8 mm 1:0 m 1:0 s
(a) 8 mm/ s = = 8000 m/s J
s 1000 mm 10 6 s

8000 m 3:281 ft 1:0 mi 3600 s
(b) 8000 m/s = = 17 900 mi/h J
s 1:0 m 5280 ft 1:0 h

1.9




1.10

L
= [A] L2 + [B] [L] [T ]
T2
1 1
) [A] = J [B] = J
LT 2 T3



1.11
(a) The dimensions of x = At2 Bvt are

[L] = [A][T 2 ] [B][LT 1 ][T ]
) [A] = [LT 2 ] J [B] = [1] (dimensionless) J




2
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, Bt
(b) The dimensions of x = Avte are

[L] = [A][LT 1 ][T ]e[B][T ]
[B][T ] = [1] ) [B] = [T 1 ] J
[L] = [A][LT 1 ][T ] ) [A] = [1] J

1.12
d4 y L 3
= = [L ]
dx4 L4
!2 [T 2]
[M L 1
] M
y = [L] =
D [F L2 ] T 2 F L2
2
Substituting [F ] = M LT —see Eq. (1.2b)— we get

!2 M T2 3
y = = [L ] Q.E.D.
D T 2 L2 ML
2
Substituting [F ] = M LT —see Eq. (1.2b)— we get

!2 M T2 3
y = = [L ] Q.E.D.
D T 2 L2 ML

1.13
The argument of the sine function must be dimensionless:
Bx L 2
= [1] [B][L] = [1] [B] = [F L ] J
k F
[F ] = [Akx2 ] = [A][F L 1
][L2 ] [A] = [L 1
]J

1.14
550 lb ft/s
(a) 110 hp = 110 hp = 60 500 lb ft/s J
1:0 hp

0:7457 kW
(b) 110 hp = 110 hp = 82:0 kW J
1:0 hp

1.15
mA mB (12)(12)
F = G 2
= (6:67 10 11 ) = 6:003 10 8 N
R 0:42
W = mg = (12)(9:81) = 117:7 N
F 6:003 10 8
% of weight = 100% = 100% = 5:10 10 8 % J
W 117:7




3
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, 1.16




1.17
0:3048 m
h = (28 000 ft) = 8534 m = 8:534 km
1:0 ft

GMe m GMe m
On earth: We = At elevation h: W =
Re2 (Re + h)2

Re2 63782
W = We 2
= 170 = 169:5 lb I
(Re + h) (6378 + 8:534)2

1.18

GMm GMe
gm = 2
ge =
Rm Re2
2
gm Mm R e 0:07348(6378)2 1
= 2
= = 0:1658 Q.E.D.
ge Me R m 5:974(1737)2 6

1.19




1.20
GMe m GMe m
On earth: We = At elevation h: W =
Re2 (Re + h)2




4
© 2017 Cengage Learning®. May not be scanned, copied or duplicated, or posted to a publicly accessible website, in whole or in part.