Math Problem Statement

Find the area of the surface generated by revolving the curve x = y^3 / 2, 0 ≤ y ≤ 3, about the y-axis.

Solution

We are tasked with finding the area of the surface generated by revolving the curve x=y32x = \frac{y^3}{2} for 0y30 \leq y \leq 3 about the y-axis.

Formula for Surface Area of Revolution:

To compute the surface area when a curve is revolved around the y-axis, we use the formula: A=2πabx1+(dxdy)2dyA = 2\pi \int_{a}^{b} x \sqrt{1 + \left(\frac{dx}{dy}\right)^2} \, dy Where:

  • x=f(y)x = f(y) is the function in terms of yy,
  • dxdy\frac{dx}{dy} is the derivative of xx with respect to yy,
  • [a,b][a, b] is the range of yy-values (here, 0 to 3).

Step-by-step Solution:

  1. Function and Derivative: The curve is given as: x=y32x = \frac{y^3}{2} Differentiate xx with respect to yy: dxdy=ddy(y32)=3y22\frac{dx}{dy} = \frac{d}{dy} \left( \frac{y^3}{2} \right) = \frac{3y^2}{2}

  2. Set up the Integral: Now, substitute x=y32x = \frac{y^3}{2} and dxdy=3y22\frac{dx}{dy} = \frac{3y^2}{2} into the surface area formula: A=2π03y321+(3y22)2dyA = 2\pi \int_0^3 \frac{y^3}{2} \sqrt{1 + \left(\frac{3y^2}{2}\right)^2} \, dy Simplifying the square term: 1+(3y22)2=1+9y44=4+9y441 + \left( \frac{3y^2}{2} \right)^2 = 1 + \frac{9y^4}{4} = \frac{4 + 9y^4}{4} Thus, the integral becomes: A=2π03y324+9y44dy=π03y34+9y44dyA = 2\pi \int_0^3 \frac{y^3}{2} \sqrt{\frac{4 + 9y^4}{4}} \, dy = \pi \int_0^3 y^3 \sqrt{\frac{4 + 9y^4}{4}} \, dy Factor the square root: A=π03y34+9y42dyA = \pi \int_0^3 y^3 \cdot \frac{\sqrt{4 + 9y^4}}{2} \, dy Which simplifies to: A=π203y34+9y4dyA = \frac{\pi}{2} \int_0^3 y^3 \sqrt{4 + 9y^4} \, dy

Now, we can solve this integral either through numerical methods or by further simplifying, but we’ll use a numerical approach to compute the exact value.

Let me calculate the value of the integral.The surface area of the surface generated by revolving the curve x=y32x = \frac{y^3}{2}, for 0y30 \leq y \leq 3, about the y-axis is approximately 577.04 square units.

Would you like further details on the calculation, or do you have any other questions?

Here are some related questions to explore:

  1. How is the formula for surface area of revolution derived?
  2. How would the surface area change if the curve were revolved around the x-axis instead?
  3. What is the effect of changing the range of yy-values on the surface area?
  4. Can this problem be solved using a parametric approach?
  5. How does the surface area formula differ for revolution around lines other than the y-axis?

Tip: When dealing with integrals involving square roots, sometimes it's helpful to check if a substitution can simplify the expression.

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Math Problem Analysis

Mathematical Concepts

Calculus
Surface Area of Revolution
Integration

Formulas

Surface Area of Revolution formula: A = 2π ∫[a,b] x sqrt(1 + (dx/dy)^2) dy

Theorems

Surface Area of Revolution
Derivative of Power Functions

Suitable Grade Level

Undergraduate Calculus or Advanced High School Calculus