Calculating Inertia in 3D: What You Need to Know

  • Thread starter Isawyou0
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    3d Inertia
In summary, The formula provided calculates the second moment of area for a general polygon in 2D using the (x,y) coordinates of the vertices. The properties of moment of inertia and mass moment of inertia are different and have different units. The second moment of area is sometimes referred to as the moment of inertia for plane figures, while the mass moment of inertia determines the ease of acceleration in rotation for 3D bodies. It is important to specify which property is being calculated in 3D as they are not the same.
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  • #2
Isawyou0 said:
Hi!
is there anyway to calculate inertia in 3d?
for all forms, like we do in 2d, is it the same?

https://upload.wikimedia.org/math/d/d/3/dd3b5877d05c86142f03703ac1c6562b.png
The formula you attached appears to calculate the second moment of area of a general polygon, using the (x,y) coordinates of the vertices.

You'll have to be more specific about what you mean by "calculat(ing) inertia in 3d".
 
  • #3
the moment of inertia in 3d is it the same for 2d?
 
  • #4
Isawyou0 said:
the moment of inertia in 3d is it the same for 2d?
It depends.

The second moment of area is sometimes referred to as the moment of inertia. This is a property of plane figures.

The mass moment of inertia for 3-D bodies determines how easy or how difficult it is to accelerate a body in rotation.

As I asked before, which of these two properties do you wish to calculate in 3-D?
 
  • #5
so there is second moment of inertia and moment of inertia I didn't knew that :/
of course I'm talking about second moment of inertia in 3d, for different shapes...
 
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  • #6
Isawyou0 said:
so there is second moment of inertia and moment of inertia I didn't knew that :/
of course I'm talking about second moment of inertia in 3d, for different shapes...
No, you have confused things.

1. There is a second moment of area for plane shapes, which is also referred to as a moment of inertia. The second moment of area has units of L4.

https://en.wikipedia.org/wiki/List_of_area_moments_of_inertia

2. There is a mass moment of inertia for 3-D bodies, which has units of ML2:

https://en.wikipedia.org/wiki/List_of_moments_of_inertia
 

1. What is inertia in 3D?

Inertia in 3D refers to the resistance of an object to changes in its motion in three-dimensional space. It is a measure of an object's mass and its distribution in space.

2. Why is it important to calculate inertia in 3D?

Calculating inertia in 3D is important in understanding the behavior and stability of an object in motion. It is also crucial in designing and engineering structures, vehicles, and machines that require precise control and movement.

3. How is inertia calculated in 3D?

Inertia in 3D is calculated using the moment of inertia formula, which takes into account an object's mass, shape, and distribution. The formula is I = ∫V r2ρ dV, where I is the moment of inertia, r is the distance from the axis of rotation, ρ is the density, and dV is the differential volume element.

4. What are some applications of calculating inertia in 3D?

Calculating inertia in 3D has numerous applications in various fields such as physics, engineering, and robotics. It is used in designing vehicles and aircraft, analyzing the stability of structures and buildings, and developing control systems for robots and other automated machines.

5. Are there any challenges in calculating inertia in 3D?

One of the main challenges in calculating inertia in 3D is accurately determining the mass distribution of an object. This requires precise measurements and calculations, especially for complex and irregularly shaped objects. Additionally, the calculation of inertia in certain scenarios, such as rotating bodies and systems with multiple axes of rotation, can be more complicated and may require advanced mathematical techniques.

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