Need help with 2 questions (#13 and #7). The answer for #13 is E and the answer

Question

Need help with 2 questions (#13 and #7). The answer for #13 is E and the answer for #7 is D. Couldn't get them when I attempted. Please show all work and steps, thank you :) 13. An ice skater with moment of inertia Io is spinning with angular speed wo. She pulls her arms in, decreasing her moment of inertia to lo/3. What is her final angular speed wy? a) wf=wo/3 e) wf = 300 While spinning down from 500.0 rotations per minute (rpm) to rest, a solid uniform flywheel does 5.1 kilo-Joules of work. If the radius of the disk is 1.2 m what is its mass? 14. a) 5.2 kg b) 4.4 kg c) 6.0 kg d) 6.8 kg e) It is not possible to determine mass with information given. 15. A uniform solid cylindrical log begins rolling without slipping down a ramp that rises 28.0° above the horizontal. After it has rolled 4.20 m along the ramp, what is the magnitude of the linear acceleration of its center of

Explanation / Answer

13) According to law of conservation of angular momentum , Angular momentum L = Iw is always constant.

That means I0W0 = If Wf

Hence Wf = (I0W0) / If = (I0W0)/ (I0/3) = 3W0

Hence option (E) is the correct answer.

Please post question no (7) separately .

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