Math Problem Statement

Region R bounded by y = √ x, y = 0, x = 5, rotated about the x-axis

Solution

The region RR is bounded by the curves y=xy = \sqrt{x}, y=0y = 0, and x=5x = 5. When this region is rotated about the x-axis, we can use the method of disks to find the volume of the solid generated.

Step 1: Identify the boundaries

The curve is y=xy = \sqrt{x}, and the boundaries are y=0y = 0 (the x-axis) and x=5x = 5. We will rotate the region from x=0x = 0 to x=5x = 5 about the x-axis.

Step 2: Set up the formula for the volume

The volume of the solid generated by rotating a region about the x-axis can be calculated using the disk method. The formula for the volume is:

V=πab[f(x)]2dxV = \pi \int_{a}^{b} [f(x)]^2 \, dx

In this case, f(x)=xf(x) = \sqrt{x}, a=0a = 0, and b=5b = 5.

Step 3: Set up the integral

Substitute f(x)=xf(x) = \sqrt{x} into the formula:

V=π05(x)2dxV = \pi \int_{0}^{5} (\sqrt{x})^2 \, dx

Since (x)2=x(\sqrt{x})^2 = x, the integral becomes:

V=π05xdxV = \pi \int_{0}^{5} x \, dx

Step 4: Solve the integral

Now, integrate xx with respect to xx:

xdx=x22\int x \, dx = \frac{x^2}{2}

Evaluate the integral from 0 to 5:

= \pi \left( \frac{5^2}{2} - \frac{0^2}{2} \right) = \pi \left( \frac{25}{2} \right)$$ ### Step 5: Calculate the volume Now multiply by $$\pi$$: $$V = \frac{25\pi}{2}$$ Thus, the volume of the solid is: $$V = \frac{25\pi}{2} \, \text{cubic units}$$ --- Would you like any further clarification or details on this problem? ### Related Questions: 1. How would the result change if the region were rotated about the y-axis instead? 2. Can we use the shell method to solve this problem instead of the disk method? 3. How would the volume differ if the upper bound for $$x$$ were 10 instead of 5? 4. What if the curve was $$y = x^2$$ instead of $$y = \sqrt{x}$$? 5. How do we calculate the surface area of the solid generated by rotating this region? ### Tip: When using the disk or washer method, always check whether the function should be squared before integrating for volume, as this represents the area of the circular cross-sections.

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Math Problem Analysis

Mathematical Concepts

Calculus
Volume of Solids of Revolution
Disk Method
Definite Integrals

Formulas

Volume = π ∫[a to b] [f(x)]^2 dx
f(x) = √x
∫ x dx = (x^2) / 2

Theorems

Disk Method for Volume of Solids of Revolution

Suitable Grade Level

Grades 11-12, College Calculus