A figure skater can increase her spin rotation rate from an initial rate of 1.0 rev every 1.2 s to a final rate of 2.0 rev/s .
PART A If her initial moment of inertia was 4.9 kg⋅m2 , what is her final moment of inertia? Express your answer using two significant figures.
PART B How does she physically accomplish this change?
Q2
A person of mass 75 kg stands at the center of a rotating merry-go-round platform of radius 3.1 m and moment of inertia 940 kg⋅m2 . The platform rotates without friction with angular velocity 0.80 rad/s . The person walks radially to the edge of the platform.
PART A
Calculate the angular velocity when the person reaches the edge.
PART B
Calculate the rotational kinetic energy of the system of platform plus person before the person's walk.
Express your answer using two significant figures.
PART C
Calculate the rotational kinetic energy of the system of platform plus person after the person's walk.
Express your answer using two significant figures.
Q1.
(A)
wi = 1 rev/1.2 s = 0.83 rev/ s
wf = 2 rev/s
Ii = 4.9 kg.m2
If = ?
Angular momentum conservation :
Iiwi = Ifwf
If = 0.83 x 4.9 / 2 = 2.03 kg.m2
(B)
She can accomplish this change by folding her hands. as mass will be nearer to axis of rotation and moment of inertia will be lesser.
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