Find the mass and center of mass of the lamina

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Discussion Overview

The discussion revolves around finding the mass and center of mass of a lamina defined by a specific region and density function. Participants explore the mathematical formulation necessary to compute these values, including the integration required for both mass and center of mass calculations.

Discussion Character

  • Mathematical reasoning

Main Points Raised

  • One participant states the mass of the lamina is calculated to be 7/3 but expresses uncertainty about finding the center of mass.
  • Another participant provides the formulas for mass and center of mass, indicating that mass is computed using a double integral over the region D with the given density function.
  • A participant reiterates the formulas for the center of mass and shares their computed center of mass as (80/9, 0), questioning its correctness.
  • A further response requests the participant to show their working to identify potential errors in their calculations.

Areas of Agreement / Disagreement

There is no consensus on the correctness of the computed center of mass, as one participant believes their result is incorrect, while another seeks clarification through detailed working.

Contextual Notes

The discussion does not resolve the specific steps or assumptions involved in the integration process for finding the center of mass, leaving the calculations open to interpretation and further exploration.

carl123
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Find the mass and center of mass of the lamina that occupies the region D and has the given density function ρ.
D = {(x, y) | 0 ≤ x ≤ 1, −1 ≤ y ≤ 1}; ρ(x, y) = 7xy2

I got my mass to be 7/3 but I'm not sure how to go about finding the center of mass
 
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The mass of the lamina is given by the formula $$m=\iint_D \rho (x, y)dA$$ and the center of mass of the lamina is $(\overline{x}, \overline{y})$ where $$\overline{x}=\frac{1}{m}\iint_D x \rho (x, y)dA \ \ \text{ and } \ \ \overline{y}=\frac{1}{m} \iint_D y \rho (x, y)dA$$
 
mathmari said:
the center of mass of the lamina is $(\overline{x}, \overline{y})$ where $$\overline{x}=\frac{1}{m}\iint_D x \rho (x, y)dA \ \ \text{ and } \ \ \overline{y}=\frac{1}{m} \iint_D y \rho (x, y)dA$$

Thanks for your reply, I got (80/9 , 0) as my center of mass but it appears to be wrong, not sure why
 
carl123 said:
Thanks for your reply, I got (80/9 , 0) as my center of mass but it appears to be wrong, not sure why

If you show your working, then perhaps it can be found where you went wrong, and how to correct it. If you simply say, "I got such and such and it is wrong, but I don't know why," this doesn't give us anything with which we can help. :)
 

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