Solution

ID: past-exam-of-the-physics-a-course-of-the-university-of-cambridge/2018/paper-1/section-a/a4/solution

Substitution in the moment of inertia gives
For independent errors interpreted as standard uncertainties, logarithmic differentiation and propagation of uncertainty give
Consequently
This is a statistical precision requirement. If “accuracy” instead means hard bounds whose worst cases must be guaranteed, first-order absolute errors add: , giving to first order. For an exact symmetric hard bound about the nominal values, the upper extreme is slightly more restrictive: gives , or . The question does not distinguish a statistical uncertainty from a worst-case tolerance, so the convention matters.

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