The rotational inertia of a collapsing spinning star drops to 1/2 its initial va

Question

The rotational inertia of a collapsing spinning star drops to 1/2

its initial value. What is the ratio of the new rotational kinetic energy to the initial rotational kinetic energy?

The rotational inertia of a collapsing spinning star drops to ts initial value. What is the ratio of the new rotational kinetic energy to the initial rotational kinetic energy? KE 1/2 KE The angular momentum of the star must be conserved because there is no external torque to change it. Angular momentum of a rigid body about a fixed axis is the product of the tional inertia of a solid sphere (the star) about its central axis is given in the table of some rotational inertias angular speed and the rotational inertia The

Explanation / Answer

Given that

Iinitial/Ifinial=2

so basing on concept of angular momentum

I1W1=I2W2

now we find the angular velocity ratio of initial and finial

W2/W1=I1/I2=2/1

now we find the kinetic energy ratio

K.E new/K.Ei=I2W2^2/I1W1^2

=(I2/I1)*(W2/W1)^2

=(1/2)*(2/1)^2

=4/2

=2

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