An ice figure skater starts out spinning at 0.85 revolution per second with her arms outstretched, as shown in Figure P12.41. She wears lightly weighted bracelets to enhance the spin-up effect when she pulls her arms in.

(a) Calculate her final rotational speed if her rotational inertia is \(3.6 \mathrm{~kg} \cdot \mathrm{m}^{2}\) with her arms outstretched and \(1.1 \mathrm{~kg} \cdot \mathrm{m}^{2}\) with her arms pulled close to her body.

(b) Determine the increase in her rotational kinetic energy.

(c) Where does this added energy come from?

Data from Figure P12.41

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