Hollow Sphere Inertia in Cartesian Coordinates

In summary, the problem is to calculate the rotational inertia of a hollow sphere in cartesian (x,y) coordinates. The relevant equation is I=Mr^2. The teacher is struggling to solve this and has asked for help from the class. The calculation may be awkward, but not too difficult. The teacher has not specified any constraints or the thickness of the sphere wall. The student is unsure how to do the calculation and will ask for more information.
  • #1
colemc20
4
0
Homework Statement
How do you calculate the rotational inertia of a hollow sphere in cartesian (x,y) coordinates?
Relevant Equations
I=Mr^2
Problem Statement: How do you calculate the rotational inertia of a hollow sphere in cartesian (x,y) coordinates?
Relevant Equations: I=Mr^2

My physics teacher said its his goal to figure this out before he dies. He has personally solved all objects inertias in cartesian coordinates but can't figure out a hollow sphere's. He said if anyone in the class can help he'd forever be in debt to them and I just genuinely want to help. Do any of you know how to do this?
 
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  • #2
That's a sad story. The calculation does seem awkward to do in Cartesian coordinates, but not too difficult. How would you set up the integral yourself? And what constraints are there on the hollow sphere? What is the thickness of the sphere wall compared to the radius?
 
  • #3
colemc20 said:
Problem Statement: How do you calculate the rotational inertia of a hollow sphere in cartesian (x,y) coordinates?
Relevant Equations: I=Mr^2
And just to be clear, you mean (x,y,z) coordinates for the sphere, correct? :wink:
 
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  • #4
berkeman said:
And just to be clear, you mean (x,y,z) coordinates for the sphere, correct? :wink:
Haha yes!
 
  • #5
berkeman said:
And just to be clear, you mean (x,y,z) coordinates for the sphere, correct? :wink:
Honestly I myself am not entirely sure how to do it. I’ll ask him in school tomorrow for extra information. I am not sure what he wants the thickness. I’m also not sure if he cares I think he just wants to know how to do it in general.
 

What is a hollow sphere?

A hollow sphere is a three-dimensional shape that is completely empty on the inside, with a spherical outer surface.

What is inertia?

Inertia is the tendency of an object to resist changes in its state of motion. It is a property of matter that causes objects to maintain their current state of motion.

How is inertia related to a hollow sphere?

Inertia is related to a hollow sphere because the distribution of mass in the sphere affects its resistance to changes in motion. The further away the mass is from the center, the greater the inertia of the sphere.

What are Cartesian coordinates?

Cartesian coordinates are a system used to locate points in a plane or in space. They consist of two or three perpendicular axes, with each axis representing a different dimension (x, y, and z).

How is inertia calculated in Cartesian coordinates for a hollow sphere?

Inertia for a hollow sphere in Cartesian coordinates can be calculated using the formula I = (2/3)mr^2, where m is the mass of the sphere and r is the radius. This formula takes into account the distribution of mass in the sphere and its distance from the center of rotation.

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