Math Problem Statement

The graph shows the base of an object. Compute the value of the volume of the object, given that cross sections (perpendicular to the base) are squares. Give an exact expression or round your answer to at least two decimals.

Solution

The problem involves computing the volume of an object whose cross-sections, perpendicular to the base, are squares. The base is given as a two-dimensional shape in the xy-plane.

Step-by-Step Approach:

  1. Understanding the Base:
    The base is a polygon formed by the points (1,1)(1, 1), (3,1)(3, 1), (4,0)(4, 0), and (1,1)(1, -1).

  2. Equation for Cross-Sectional Area:
    For each value of xx, the side length of the square is determined by the distance between the top and bottom edges of the shape at that particular xx-value (the vertical height of the shape at xx).

  3. Finding the Height of the Base Shape:

    • For x[1,3]x \in [1, 3], the top boundary is y=1y = 1, and the bottom boundary is a linear function connecting (1,1)(1, -1) and (3,1)(3, 1), which has slope 1 and equation y=x2y = x - 2.
    • For x[3,4]x \in [3, 4], the top boundary is y=1y = 1, and the bottom boundary is a horizontal line y=0y = 0.
  4. Volume Formula: The volume is calculated by integrating the area of the square cross-sections over the xx-range from 1 to 4. The side length of each square is the vertical distance between the top and bottom boundaries, and the area of each square is the square of this distance. Hence, the volume is given by:

    V=14(side length at x)2dxV = \int_{1}^{4} \left( \text{side length at } x \right)^2 \, dx

    We'll split this into two integrals because the base changes at x=3x = 3.

    For 1x31 \leq x \leq 3: The side length is the distance between y=1y = 1 and y=x2y = x - 2, which is 1(x2)=3x1 - (x - 2) = 3 - x.

    For 3x43 \leq x \leq 4: The side length is the distance between y=1y = 1 and y=0y = 0, which is 10=11 - 0 = 1.

    Therefore, the volume is:

    V=13(3x)2dx+34(1)2dxV = \int_{1}^{3} (3 - x)^2 \, dx + \int_{3}^{4} (1)^2 \, dx

Let me calculate the exact value of this volume.The exact volume of the object is 113\frac{11}{3}, or approximately 3.673.67 cubic units when rounded to two decimal places.

Would you like further details on any part of the process? Here are some additional questions you could explore:

  1. How do you find the area of cross sections for other shapes, such as semicircles or triangles?
  2. What if the base of the object was a different shape? How would the approach change?
  3. Can we calculate the centroid of the base shape shown in the graph?
  4. How would you calculate the surface area of this 3D object?
  5. How would the volume change if the cross sections were not squares but equilateral triangles?

Tip: When dealing with volumes of solids with known cross-sections, always focus on the relationship between the base and the height to set up the correct integral!

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Math Problem Analysis

Mathematical Concepts

Integration
Geometry of solids
Volume by known cross-sections

Formulas

Volume = ∫(side length)^2 dx
Linear equation for height: y = mx + b

Theorems

Fundamental Theorem of Calculus
Pythagorean Theorem (for finding distances)

Suitable Grade Level

Grades 10-12