Moment of Inertia around z-axis: 1-x^2, 4x+3y+2z+12

In summary, the formula for calculating moment of inertia around the z-axis is I<sub>z</sub> = ∫(x<sup>2</sup> + y<sup>2</sup>)dm, where dm is the differential mass and x and y are the distances from the z-axis. To calculate moment of inertia for a specific shape, it can be broken down into smaller, simpler shapes and the individual moments of inertia can be added together. The moment of inertia around the z-axis is significant as it measures an object's resistance to rotational motion. The distribution of mass affects the moment of inertia, with a larger concentration of mass resulting in a larger moment of inertia. The moment of inertia cannot be negative, as
  • #1
Gidza
2
0

Homework Statement


Find the moment of inertia around the z-axis of the solid bounded by x=0, y=0,z=0,y=1-x^2 and 4x+3y+2z+12 assume density=1.


Homework Equations


please refer to my attachment.


The Attempt at a Solution


Attached
 

Attachments

  • Moment of inertia around z_axis.PDF
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  • #2
You have written 4x+3y+2z+12, which I'm interpreting as 4x+3y+2z=12 => x/3+y/4+z/6=1. (All right, now I got the correct eqn from the pdf file.)

How can x go from 0 to 3? In the 1st octant, x is from 0 to 1. The rest looks OK.
 
  • #3
Yes your assumption above was correct, and thank you for your assistance!
 

Related to Moment of Inertia around z-axis: 1-x^2, 4x+3y+2z+12

1. What is the formula for calculating moment of inertia around the z-axis?

The formula for calculating moment of inertia around the z-axis is Iz = ∫(x2 + y2)dm, where dm is the differential mass and x and y are the distances from the z-axis.

2. How do you calculate moment of inertia for a specific shape?

The moment of inertia for a specific shape can be calculated by breaking it down into smaller, simpler shapes and using the formula Iz = ∫(x2 + y2)dm for each individual shape. The individual moments of inertia can then be added together to get the total moment of inertia for the shape.

3. What is the significance of the moment of inertia around the z-axis?

The moment of inertia around the z-axis is a measure of an object's resistance to rotational motion around that axis. It is an important property in understanding the dynamics of rotating objects and is used in many engineering and physics applications.

4. How does the distribution of mass affect the moment of inertia around the z-axis?

The distribution of mass greatly affects the moment of inertia around the z-axis. Objects with a larger concentration of mass farther away from the z-axis will have a larger moment of inertia, while objects with a more spread out mass distribution will have a smaller moment of inertia.

5. Can the moment of inertia around the z-axis be negative?

No, the moment of inertia around the z-axis cannot be negative. It is always a positive value since it is calculated by squaring the distances from the z-axis. A negative value would indicate a negative mass, which is not physically possible.

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