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· Moment of Inertia
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· Newton's First Law ( Law of Inertia )
· Newton's Second Law (Law of Resultant Force )
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Current Location > Physics Formulas > Mechanics > Moment of Inertia

Moment of Inertia

The moment of inertia of is given by:

Where we have:
m: mass
R: radius ( from the axis O to the object )

The following is a list of moment of inertia for some common homogeneous objects, where M stands for mass and the red line is the axis the objects rotating about.

Object	Illustration	Moment of inertia
Particle		Md2 The distance between the particle and the axis is d.
Bar		ML2/3 The length of the bar is L
Bar		ML2/12 The length of the bar is L
Rectangular plate		ML2/12 The length of the plate is L and is orthogonal to the axis.
Rectangular plate		M(L2 + W2)/12 L is the length and W is the width
Circular plate		MR2/2 R is the radius of the ring
Circular plate		MR2/4 R is the radius of the ring
Ring		MR2 R is the radius of the ring
Cylinder		MR2/2 R is the radius of the caps
Cylinder		MR2/4 + ML2/12 R is the radius of the caps and L is the height of the cylinder
Spherical surface		2MR2/3 R is the radius
Sphere		2MR2/5 R is the radius