Moment the inertia the cube can be calculated using various equations depending on the place of the axis. Normally, there space two instances that us consider. Lock are;

When the axis of rotation is in ~ the centre. The formula is offered as;

Moment of Inertia that Cube Derivation


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To derive the minute of inertia of a cube as soon as its axis is passing with the center we have actually to think about a couple of things. We will assume the solid cube having actually mass m, elevation h, width w, and also depth d. Interestingly, the cube’s minute of inertia will certainly be comparable to that of a square lamina with side around an axis with the centre.


Now we will assume the area density of the lamina to it is in ρ. We will certainly then take it the element of the lamina v cartesian works with x, y in the plane to be dx dy. Currently we deserve to assume its mass to it is in = ρdxdy.

When we space finding the MOI us will use ρ(x2+y2) dx dy.

Next step entails integration wherein we combine over the entire lamina. Us obtain;

–-a/2∫a/2 ρ (x2+y2) dx dy = ρa4 / 6.

We will certainly then instead of the values for the mass of the lamina which is ρ =ma2.

And we obtain, ns = ma2 / 6

2. because that the second instance when the axis is passing through the leaf we will certainly understand how the source is brought out below.


First, we recall the equation for moment of inertia. The is composed as;

I = ∫ r2dm

Now because we require to discover the MOI around an axis through the edge, we will certainly take the z-axis.

Moving forward, we have actually to consider the cube come be broken down right into infinitesimally tiny masses. We have the right to then assume their sizes to be dy, dx, and dz. With this we get;

dm = ρ dxdydz

Here, ρ = density.

If we look in ~ the minute of inertia formula given above we have actually r as well. It is nothing however the street from the z-axis come mass dm. Think about the works with of the mass ‘dm’ to be x,y, and z). Currently the distance ‘r’ will be;

r= √ x2 + y2

r2 = x2 + y2

Meanwhile, the worth of x,y, and z will variety from O come b according to the length of the edges.

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We will now substitute the worths that we have gained so much in the minute of inertia equation and also carry the end the integration.