10.84:
(a)
2
2
2
s
rad
92
.
0
m
00
.
8
60
cos
)
s
m
80
.
9
(
2
3
L
cos
2
3
3
1
cos
2
1
=
°
=
θ
=
α
α
=
θ
=
Σ
g
mL
mg
Iα
τ
(b) As the bridge lowers,
is
so
changes,
α
θ
not constant. Therefore Eq. (9.17) is
not valid.
(c) Conservation of energy:
s
rad
78

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