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62. We treat the ballerina as a rigid object rotating around a fixed axis, initially and then
again near maximum height. Her initial rotational inertia (trunk and one leg extending
outward at a 90
°
angle) is
22
2
trunk
leg
0.660 kg m
1.44 kg m
2.10 kg m .
i
II
I
=+
=
⋅
+
⋅
=
⋅
Similarly, her final rotational inertia (trunk and
both
legs extending outward at a
30
θ
=°
angle) is
2
2
2
trunk
leg
2
sin
0.660 kg m
2(1.44 kg m )sin 30
1.38 kg m ,
f
I
=
⋅
+
⋅
°
=
⋅
where we have used the fact that the effective length of the extended leg at an angle
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This note was uploaded on 05/17/2011 for the course PHY 2049 taught by Professor Any during the Spring '08 term at University of Florida.
 Spring '08
 Any
 Physics, Inertia

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