- #1

jaewonjung

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- Homework Statement
- A rigid rod of mass M and length L has moment of inertia 1/12 ML^2 about its center of mass. A sphere of mass m and radius R has moment of inertia 2/5 MR^2 about its center of mass. A combined system is formed by centering the sphere at one end of the rod and placing an axis at the other.

What is the moment of inertia of the combined system?

- Relevant Equations
- SumI=I1+I2+I3...

I=MR^2

Moment of inertia for a rod rotated around one end is 1/3ML^2 using the parallel axis theorem

Moment of inertia for a sphere is 2/5 MR^2

Itotal=Isphere+Irod=2/5MR^2+1/3ML^2

However, the answer is 2/5MR^2+1/3ML^2+ML^2

Why is there an extra ML^2 added to the moment of inertia?

Moment of inertia for a sphere is 2/5 MR^2

Itotal=Isphere+Irod=2/5MR^2+1/3ML^2

However, the answer is 2/5MR^2+1/3ML^2+ML^2

Why is there an extra ML^2 added to the moment of inertia?