alleryStart learning →How is the moment of inertia of an extended body built up, and what does it depend on?
AProduct of m and r, and on the body speed
BSum of m r squared, and on nothing else
CSum of m times r, and on the chosen axis
DSum of m r squared, and on the chosen axis
Answer & Solution
Correct answer: D. Sum of m r squared, and on the chosen axis
1. Any object can be treated as a collection of point masses.
2. Each point mass contributes m r squared, so the total is I = sum of m r squared.
3. Every r is measured from the axis, so the answer changes if the axis changes.
4. A moment of inertia quoted without naming its axis is therefore incomplete.
_Source: OpenStax College Physics (CC BY 4.0), Ch 10 "Rotational Motion and Angular Momentum", section 10.3 Dynamics of Rotational Motion: Rotational Inertia_
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