Try it on paper first. A hint, the key idea and the worked solution are here when you need them.
Masses of and are fixed to the ends of a light rod long. Find the moment of inertia about an axis at right angles to the rod through
Moment of inertia: . Ring ; disc ; rod about its middle; solid sphere . Parallel axes: . Flat bodies: .
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Plan. Add for each mass.
Step 1. (a) .
Step 2. (b) .
Step 3. (c) Distances and : .
Answer: (a) . (b) . (c) .
Check. Parallel axes: . It agrees with (a).
Watch out. The moment of inertia is smallest about the centre of mass, as the parallel axis theorem says.
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