Math Problem Statement

Find the mass and center of mass of the lamina with the given density.

Lamina bounded by y = x2 − 7 and y = 42, ρ(x, y) = square of the distance from the y−axis. Enter exact answers, do not use decimal approximations.

Solution

To solve this problem, we'll need to find both the mass and the center of mass of the lamina. Here's how we will approach it:

Step 1: Boundaries of the Region

We are given that the lamina is bounded by the curves y=x27y = x^2 - 7 and y=42y = 42. The first step is to find the points where these curves intersect, which will give us the limits for the region over which we integrate.

Set y=x27y = x^2 - 7 equal to y=42y = 42:

x27=42x^2 - 7 = 42 x2=49x^2 = 49 x=±7x = \pm 7

So, the region is bounded between x=7x = -7 and x=7x = 7.

Step 2: Mass of the Lamina

The mass MM of the lamina is given by:

M=Rρ(x,y)dAM = \iint_R \rho(x, y) \, dA

where ρ(x,y)=x2\rho(x, y) = x^2 is the density function (square of the distance from the y-axis), and dAdA is the area element. We can express this double integral as an iterated integral in terms of xx and yy.

For a given xx, yy ranges from y=x27y = x^2 - 7 to y=42y = 42, and xx ranges from 7-7 to 77. So, the mass integral becomes:

M=77x2742x2dydxM = \int_{-7}^{7} \int_{x^2 - 7}^{42} x^2 \, dy \, dx

Step 3: Center of Mass Coordinates

The coordinates x\overline{x} and y\overline{y} of the center of mass are given by:

x=1MRxρ(x,y)dA=1MRxx2dA=1MRx3dA\overline{x} = \frac{1}{M} \iint_R x \rho(x, y) \, dA = \frac{1}{M} \iint_R x \cdot x^2 \, dA = \frac{1}{M} \iint_R x^3 \, dA y=1MRyρ(x,y)dA=1MRyx2dA\overline{y} = \frac{1}{M} \iint_R y \rho(x, y) \, dA = \frac{1}{M} \iint_R y \cdot x^2 \, dA

Thus, we will need to compute these two integrals to find x\overline{x} and y\overline{y}.

Step 4: Solve the Integrals

Let me compute the integrals for the mass MM, x\overline{x}, and y\overline{y}.It seems like I can’t do more advanced data analysis right now. Please try again later.

Would you like help with another aspect of this problem or a breakdown of how you could calculate these integrals by hand? Let me know if you have any questions.

Here are five related questions that could deepen your understanding:

  1. How do we find mass and center of mass for lamina with a different density function?
  2. What if the lamina was bounded by other curves, such as parabolas or lines?
  3. How do you calculate the center of mass for 3D objects with non-uniform density?
  4. What does it mean when the center of mass is located outside the object itself?
  5. How do the concepts of center of mass and moment of inertia relate to each other?

Tip: When working with integrals in physics, it helps to first sketch the region and get a visual feel for the problem before setting up the limits of integration.

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Math Problem Analysis

Mathematical Concepts

Calculus
Double Integrals
Center of Mass
Mass of Lamina
Density Functions

Formulas

Mass: M = ∬_R ρ(x, y) dA
Center of Mass (x): x̄ = (1/M) ∬_R xρ(x, y) dA
Center of Mass (y): ȳ = (1/M) ∬_R yρ(x, y) dA

Theorems

The Concept of Center of Mass in Calculus
Application of Double Integrals for Mass Calculation

Suitable Grade Level

College Level Calculus (Grades 12+)