Math Problem Statement

The solid with a semicircular base of radius 11 whose cross sections perpendicular to the base and parallel to the diameter are squares. find volune

Solution

To find the volume of a solid with a semicircular base of radius 11, whose cross-sections perpendicular to the base and parallel to the diameter are squares, we can use the following method:

Step-by-Step Approach:

  1. Equation of the semicircle:
    Since the base is a semicircle, the equation of the semicircle (with radius 1111) in the xyxy-plane is: y=112x2=121x2y = \sqrt{11^2 - x^2} = \sqrt{121 - x^2} where xx ranges from 11-11 to 1111.

  2. Area of the cross-section:
    The cross-sections perpendicular to the base and parallel to the diameter are squares. The side length of each square is equal to the height of the semicircle at a given xx, which is 2y=2121x22y = 2\sqrt{121 - x^2}.

    Therefore, the area of the square at a particular xx is: A(x)=(2121x2)2=4(121x2)=4844x2A(x) = \left( 2\sqrt{121 - x^2} \right)^2 = 4(121 - x^2) = 484 - 4x^2

  3. Volume by integration:
    To find the total volume, we integrate the area of the square cross-sections along the base of the semicircle from x=11x = -11 to x=11x = 11: V=1111A(x)dx=1111(4844x2)dxV = \int_{-11}^{11} A(x) \, dx = \int_{-11}^{11} (484 - 4x^2) \, dx

  4. Evaluate the integral:
    We can break the integral into two parts: V=1111484dx11114x2dxV = \int_{-11}^{11} 484 \, dx - \int_{-11}^{11} 4x^2 \, dx The first integral is straightforward: 1111484dx=484(11(11))=48422=10,648\int_{-11}^{11} 484 \, dx = 484 \cdot (11 - (-11)) = 484 \cdot 22 = 10,648 The second integral is: 11114x2dx=4[x33]1111=4(1133(11)33)=4(11331133)=0\int_{-11}^{11} 4x^2 \, dx = 4 \cdot \left[ \frac{x^3}{3} \right]_{-11}^{11} = 4 \cdot \left( \frac{11^3}{3} - \frac{(-11)^3}{3} \right) = 4 \cdot \left( \frac{11^3}{3} - \frac{11^3}{3} \right) = 0 Since the x2x^2 term is an even function, the integral over symmetric limits cancels out to zero.

    Therefore, the total volume is: V=10,648V = 10,648

Thus, the volume of the solid is 10,648 cubic units.


Would you like further details on any of these steps?

Here are five related questions for further exploration:

  1. What is the formula for finding volumes of solids with different cross-sectional shapes?
  2. How would the volume change if the base were a full circle rather than a semicircle?
  3. Can this method be applied to cross-sections that are equilateral triangles instead of squares?
  4. How does the shape of the base affect the volume of a solid?
  5. What happens if the radius of the semicircular base is doubled?

Tip: When dealing with volume problems, always check if you can simplify the cross-sectional area function to make integration easier.

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Math Problem Analysis

Mathematical Concepts

Geometry
Calculus
Volume of Solids of Revolution

Formulas

Equation of semicircle: y = sqrt(121 - x^2)
Area of cross-section: A(x) = 4(121 - x^2)
Volume by integration: V = ∫ from -11 to 11 (484 - 4x^2) dx

Theorems

Method of Cross-Sections
Integral Calculus

Suitable Grade Level

Grades 11-12, College Level Calculus