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# What Are the Units for Moment of Inertia?

**The SI units for moment of inertia are kg m^2.** For a point mass, the moment of inertia equals mass times radius squared, so other mass units (such as pounds) and other distance units (such as feet) are occasionally used instead.

A specific axis of rotation must be defined to calculate the moment of inertia since it measures an object's resistance to a change in rotational direction. Multiple point masses or continuous objects have a moment of inertia that is the sum of all the point masses within the object. For continuous objects this is found by integration. There are known formulas to calculate the moment of inertia for common shapes like cylinders or rods.

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Q:
## What Is the Parallel Axis Theorem?

A: The parallel axis theorem states that the "moment of inertia of any object about an axis through its center of mass is the minimum moment of inertia for an... Full Answer >Filed Under: -
Q:
## What Is the Moment of Inertia of a Sphere?

A: The moment of inertia of a sphere is I = 2/5 MR^2 for a solid sphere and I = 2/3 MR^2 for a thin spherical shell. This moment of inertia can be derived fro... Full Answer >Filed Under: -
Q:
## How Do You Calculate the Moment of Inertia of a Rod?

A: Calculating the moment of inertia for a rod requires you to know the mass, length and location of the rotational axis. An estimation may be required with r... Full Answer >Filed Under: -
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## What Is the Formula That Is Used to Calculate Rotational Inertia Units?

A: The formula used to determine inertia is "I= mr²," where "I" is the rotational inertia unit, "m" is the mass of a single point of movement and "r" is the d... Full Answer >Filed Under: