Center of Mass (Triple Integral)

In summary, the solid T is a cylinder with a radius of 2 and extends from the yz-plane to x=3. The center of mass of T can be found by setting up an integral from x=0 to x=3, y= -2 to y=2, and z= -√(4-y^2) to z=√(4-y^2), with a constant density of πr^2. The integral of x can be integrated to determine the density.
  • #1
Reefy
63
1

Homework Statement



T is the solid bounded by the cylinder y^2+z^2=4 and the planes x=0 and x=3. The mass density at a point P of T is directly proportional to the distance between P and the yz-plane.

Find the center of mass of the solid T.

Homework Equations



y^2+z^2=4

x=0

x=3

The Attempt at a Solution



I drew the solid and got a cylinder extending from x=0 (yz-plane) all the way to x=3 with a radius of 2.

I also attempted to set up an integral but I think my main problem is figuring out what the density to integrate is.

I set up my integral as the integral from x=0 to x=3, the integral from y= -2 to y=2, and the integral from
z= -√(4-y^2) to z=√(4-y^2) dz dy dx.

Is that correct? I don't know how to go about determining my p(x,y,x) aka my density.Edit: Initially I tried to use x as my density but I couldn't integrate that so I tried y and then z but none of them worked out.
 
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  • #2
No one knows? :confused:
 
  • #3
Hi Reefy! :smile:

(try using the X2 button just above the Reply box :wink:)
Reefy said:
I set up my integral as the integral from x=0 to x=3, the integral from y= -2 to y=2, and the integral from
z= -√(4-y^2) to z=√(4-y^2) dz dy dx.

Is that correct?

Yes :smile:

(but in this case the density is constant over each circular slice, so you could just use πr2, and integrate only over x :wink:)
I don't know how to go about determining my p(x,y,x) aka my density.

Edit: Initially I tried to use x as my density but I couldn't integrate that …

You can't integrate ∫ x dx ? :confused:

(or ∫∫∫ x dxdydz)
 

FAQ: Center of Mass (Triple Integral)

1. What is the concept of center of mass?

The center of mass is a point in a system where the mass of the object or system is evenly distributed. It is the point where the total weight of the object can be considered to be concentrated.

2. How is the center of mass calculated?

The center of mass can be calculated using a triple integral, which involves integrating the mass density function over the three dimensions of a coordinate system. The formula for center of mass is (x̄, ȳ, z̄) = (∫∫∫ xρ dV, ∫∫∫ yρ dV, ∫∫∫ zρ dV) / (∫∫∫ ρ dV), where ρ is the mass density function and dV is the volume element.

3. What is the importance of the center of mass in physics?

The center of mass is an important concept in physics because it helps determine the overall motion and behavior of an object or system. It is used in many calculations, such as determining the stability of an object, predicting its trajectory, and understanding rotational motion.

4. How does the center of mass relate to the center of gravity?

The center of mass and center of gravity are often used interchangeably, but they are slightly different concepts. The center of mass is a point based on the distribution of mass, while the center of gravity is a point where the force of gravity can be considered to act on an object. In a uniform gravitational field, the center of mass and center of gravity will be the same point.

5. Can the center of mass be outside of an object?

Yes, the center of mass can be outside of an object, especially in irregularly shaped objects. This can happen if the mass is distributed unevenly or if there are empty spaces within the object. In some cases, the center of mass may even be located outside of the physical boundaries of the object.

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