COSMOS: Complete Online Solutions Manual Organization System
Iζ = ∫ x 2dm
Now
and
a
Iζ = ∫ x 2dm′ = 2 ∫ 02 x 2 ( ρ tζ dx )
a
h
= 2 ρ t ∫ 02 x 2 ( a − 2 x ) dx
a
a
h a
1 2
= 2 ρ t x3 − x 4
a 3
4 0
3
h a a
1a
= 2ρ t −
a 3 2
4 2
=
(b) Have
4
1
1
ρ ta3h =
ma 2
48
24
2
I y = ∫ ry2dm = ∫ x 2 + (ζ sin θ ) dm
= ∫ x 2dm + sin 2 θ ∫ ζ 2dm
Now
I x = ∫ ζ 2dm ⇒ I y = Iζ + I x sin 2 θ
=
1
1
ma 2 + mh 2 sin 2 θ
24
6
or I y =
(c) Have
(
m 2
a + 4h 2 sin 2 θ
24
(
)
)
I z = ∫ rz2dm = ∫ x 2 + y 2 dm
2
= ∫ x 2 + (ζ cosθ ) dm
= ∫ x 2dm + cos 2 θ ∫ ζ 2dm
= Iζ + I x cos 2 θ
=
1
1
ma 2 + mh 2 cos 2 θ
24
6
or I z =
m 2
a + 4h 2 cos 2 θ
24
(
) COSMOS: Complete Online Solutions Manual Organization System
Chapter 9, Solution 129.
Mass of cylindrical ring:
m = ρV
=
=
γ π
π 2
2
d 2 − d1 t
g4
4
π γ
4 g
(d
2
2
)
− d12 t
Now treat the wheel as a series of 4 concentric rings. (Note - the steel is treated as
a large ring minus two smaller rings.)
mwheel = ∑ mring
=
π 0.310 lb/in 3
4 32.2 ft/s
+
π 0.284 lb/in 3
4 32.2 ft/s 2
−2 ×
+
(
)
× 1.5 in. × 0.7 2 − 0.52 in 2
2
(
π 0.284 lb/in 3
4 32.2 ft/s
π 0.043 lb/in 3
4 32.2 ft/s 2
)
× 1.5 in. × 4.42 − 0.7 2 in 2
2
×
1.1
in. × 42 − 1.22 in 2
2
(
(
)
)
× 1.5 in. × 52 − 4.42 in 2
(
mwheel = 2.7221 × 10−3 + 196.072 × 10−3 − 110.945 × 10−3 + 8.8730 × 10−3
= 96.722 × 10−3
) lbft⋅ s
2
lb ⋅ s 2
ft
continued
COSMOS Chapter 9 Solution 128
of 2
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