 Solution

ID: past-exam-of-the-physics-b-course-of-the-university-of-cambridge/2013/paper-1/section-a/a5/solution

M = \frac{4 π ρ}{3} (R_{2}^{3} - R_{1}^{3}), I_{c} = \frac{8 π ρ}{15} (R_{2}^{5} - R_{1}^{5}) .

R_{2}

I_{tangent} = \frac{8 π ρ}{15} (R_{2}^{5} - R_{1}^{5}) + \frac{4 π ρ}{3} (R_{2}^{3} - R_{1}^{3}) R_{2}^{2} .

It tends to

7 M R_{2}^{2} /5

5 M R_{2}^{2} /3

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