4 A ballerina is spinning on one foot with her arms stretched out, when she pulls her arms in. Will the following quantities increase, decrease or remain unchanged? (Ignore air drag)
(i) Her angular speed. Increase
(ii) Her moment of inertia. Decrease
(iii) Her angular momentum. Increase
(iii) Her rotational kinetic energy. Increase.
K1 = 1/2 I1ω1 ; K2 =
1/2 I2ω2 . Because I1ω1
= I2ω2 , it follows K2 = (1/2
I1ω1)(I1/I2) =
K1(I1/I2) >
K1
THE ANSWERS ARE IN BOLD, COULD YOU PLEASE SHOW THE WORKING
FOR THIS QUESTION?
4 A ballerina is spinning on one foot with her arms stretched out, when she pulls...
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