Name: slicing methods for solid volume
Uploaded: 2026-01-12T12:24:41.000Z
Duration: 1 min 27 s
Channel: JoVE

体积计算通常从简单的立体图形开始。对于一个长方体，其体积可通过将其底面积（即长乘以宽）乘以高来求得。然而，许多复杂的固体并不具有均匀的横截面。它们的体积必须使用一种称为切片法的强大技术来计算，该方法依赖于积分。在切片法中，将固体视为沿选定轴垂直切割而成的一叠极薄切片。每一片被近似为一个薄的立体，其横截面积由该片位置 x 的函数给出。每片的体积约为 A(x) 乘以 Δx。将这些近似值相加可得到一个黎曼和，当切片变得越来越薄时，该黎曼和转化为一个定积分。因此，通过在立体的起始点和终点之间对横截面积函数进行积分，可计算出总体积。该方法在工程中用于通过沿长度方向积分横截面积来计算不规则结构（如混凝土坝）的体积。计算所得的体积可用于估算所需的建筑材料。

利用积分计算立体的体积

Calculation of Volume of Solids by Integration

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calculation-of-volume-of-solids-by-integration

Education

教育

JoVE Core

Calculus

微积分

Unit

单元

Applications of Integration

积分的应用

KEY TERMS AND CONCEPTS

关键术语与概念

slicing methods for solid volume

Slicing methods help find the volume of solids with changing cross-sections. A basic solid, like a rectangular box, is easy to measure because its base area stays the same along its height. Many real objects do not have that regular shape, so elementary geometry is not enough.

The slicing method solves this by breaking a solid into many very thin slices. These slices are taken perpendicular to a chosen axis, often the x-axis. Each slice has a small thickness, written as delta x, and a cross-sectional area that changes with position.

Each thin slice is treated like a simple shape whose volume can be estimated. The volume of one slice is found by multiplying its cross-sectional area by its thickness. When all of the slice volumes are added, the result is a Riemann sum, which gives an approximation of the whole solid.

As the slices become thinner and more numerous, the approximation becomes more accurate. In the limit, the Riemann sum becomes a definite integral. That integral gives the exact volume by adding the cross-sectional areas across the full interval of the object.

Engineers and applied scientists use this method for irregular structures such as concrete dams. A dam may change shape along its length because of structural and geological needs. By modeling cross-sectional area as a function of position and integrating along the dam, engineers can estimate total volume and use that result to plan material needs, construction costs, and project feasibility.

Slicing Methods for Solid Volume

area between curves: integrating with respect to x

area-between-curves-integrating-with-respect-to-x

Vertical Slices for Area Between Curves

Area between curves can be found by using vertical slices and a definite integral. For two continuous functions on a closed interval from a to b, the region is bounded by their graphs on the sides and by the interval endpoints across the bottom and top edges of the setup. A first estimate comes from splitting the interval into many narrow vertical strips of equal width. Each strip is treated like a rectangle. Its height is the vertical difference between the two functions at a chosen point...

area between curves: integrating with respect to y

area-between-curves-integrating-with-respect-to-y

Horizontal Slices for Area Between Curves

Area between curves can be found with horizontal slices when both boundaries are written as functions of y. The left and right curves are continuous from y = c to y = d, and those lines set the vertical limits of the region. Because the curves depend on y, the area is best measured by moving across the shape with thin horizontal strips. The method uses a Riemann sum. The region is divided into many thin strips with the same height, delta y. For each strip, the width is the horizontal distance...

area between curves: problem solving

Piecewise Area Between Curves

Piecewise area between curves uses more than one integral to find the size of a region on a graph. In this example, the region is enclosed by a square root function, a reflected cube root function, and a linear function. The line intersects each of the other two curves, and those intersection points show where the boundary of the region changes. The area cannot be found with one setup over the full interval because the top and bottom curves are not the same everywhere. The region is split at...

calculation of volume of solids by integration

Slicing methods help find the volume of solids with changing cross-sections. A basic solid, like a rectangular box, is easy to measure because its base area stays the same along its height. Many real objects do not have that regular shape, so elementary geometry is not enough. The slicing method solves this by breaking a solid into many very thin slices. These slices are taken perpendicular to a chosen axis, often the x-axis. Each slice has a small thickness, written as delta x, and a...

volumes of solids of revolution

Disk Method for Rotated Region Volume

The disk method is used to find the volume of a solid formed by rotating a region around an axis. The region is first drawn in a two-dimensional plane. When that region spins around a fixed line, called the axis of revolution, it creates a three-dimensional shape with rotational symmetry. These shapes appear often in math models, physics, and engineering. When the region touches the axis of revolution, the solid has no hollow space inside. Its cross-sections are circular, so the shape can be...

finding volume using cross-sectional area

finding-volume-using-cross-sectional-area

Tetrahedron Volume from Triangle Slices

Tetrahedron volume can be found by adding the areas of triangular slices. This method uses cross-sectional area, which is the area of a flat slice taken through a 3D solid. It is useful when a solid changes shape in a regular way and a simple geometric formula is not available. A tetrahedron is a good example. It has a height h and an equilateral triangle base with side length a. The coordinate system places the origin at the top vertex, and the y-axis goes downward along the height to the...

problem solving: volume

Finding the Volume of a Jet Fuel Tank

The volume of a jet fuel tank can be found with solids of revolution. The tank is modeled by rotating a two-dimensional region around the x-axis. This creates a three-dimensional shape that is symmetric about the axis of rotation. The region runs from 0 to 2 meters, so the tank’s shape can be measured along that length. Because the boundary curve touches the axis, the disk method works well here. The disk method breaks the solid into many very thin circular slices that are perpendicular to the...

average value of a function

Estimating Function Behavior with Average Value

The average value of a function gives one number that summarizes how a quantity changes over a closed interval. It can also be viewed as the height of a rectangle whose area matches the net area under the curve. That net area includes both positive and negative parts of the function, so the result reflects the function’s overall behavior. A greenhouse temperature over a 24-hour period is a practical example of this idea. The temperature may rise and fall throughout the day, but it is still...

key terms and concepts

Learn how the slicing method uses cross-sectional area, Riemann sums, and definite integrals to estimate the volume of irregular solids like concrete dams.

Slicing Methods for Solid Volume | JoVE K12

The JoVE Core Calculus collection provides a comprehensive visual guide to the entire calculus sequence, seamlessly connecting mathematical theory to real-world applications in physics and economics. Through dynamic animated lessons, the course transitions smoothly from foundational single-variable concepts to advanced multivariable topics. Students will explore everything from standard differentiation and integration to spatial vectors, multi-dimensional derivatives, and complex vector fields. By breaking down abstract coordinate systems, infinite series, and spatial motion, this structured approach builds the robust analytical skills and advanced mastery essential for STEM success.

calculus

Slicing Methods for Solid Volume

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