Name: calculating surface area from rotation
Uploaded: 2026-01-12T12:24:30.000Z
Duration: 1 min 29 s
Channel: JoVE

כדי להבטיח שמנוע הרקטה עמיד בטמפרטורות קיצוניות, על המהנדסים להניח שכבה מדויקת של ציפוי עמיד לחום על הפיה בצורת פעמון שלו.הערכת כמות החומר המדויקת הנדרשת דורשת חישוב שטח הפנים הכולל של הסיבוב.נבחן את פרופיל הפיה כפונקציה מעוקלת במישור דו-ממדי. סיבוב עקומה זו סביב ציר ה-x יוצר את פני השטח התלת-ממדיים של הסיבוב.כדי לחשב את השטח המדויק, העקומה מחולקת לתתי-אינטרוולים קטנים המוקרבים על ידי קווים ישרים. הסובב כל קטע ישר סביב הציר יוצר פס חרוטי צר.שטח הפנים של רצועה אחת מחושב על ידי הכפלת ההיקף בגובה השיפוע. מכיוון שהרדיוס משתנה לאורך הרצועה, החישוב משתמש ברדיוס ממוצע.במקביל, גובה השיפוע מחושב באמצעות אורך הקשת של העקומה לאורך אותו מקטע. זה מסביר את תלילות השיפוע של הפיה.לבסוף, סכום שטחי הפסים הללו מספק קירוב. כאשר המקטעים הופכים לצרים אינסופית, הרדיוס הממוצע מתכנס לערך הפונקציה. גבול זה ממיר את הסכום לאינטגרל מוגדר, ונותן את שטח הפנים המדויק.

שטח פני שטח סיבוב

Area of a Surface of Revolution

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Education

JoVE Core

Calculus

חשבון דיפרנציאלי ואינטגרלי

Unit

יחידה

Application of Techniques of Integration

יישום של טכניקות אינטגרציה

KEY TERMS AND CONCEPTS

מונחים ומושגים מרכזיים

calculating surface area from rotation

Surfaces of revolution are created when a two-dimensional curve is rotated around an axis. The rotation produces a three-dimensional shape. In engineering, this calculation can help determine the surface area of a rocket nozzle. That information matters when a heat-resistant coating must be applied evenly.

When a curve is revolved about the x-axis, it sweeps out a continuous surface. To find its area, the curve is first broken into small straight-line pieces over short intervals. Each rotated piece forms a narrow conical band, which is a thin ring-like section of a cone. The area of each band is estimated using its average circumference and its slant height, which is the tilted length of that segment.

The radius for each band comes from the function values over the interval. The slant height comes from the arc length of the curve. As the intervals become smaller, the estimate becomes more accurate. In the limit, the surface area is written as a definite integral.

This integral includes the changing radius and the slope of the curve. It captures the true shape of the surface instead of a rough estimate. The final result gives a precise surface area value. That precision is important in high-stakes work such as thermal protection for aerospace parts.

Calculating Surface Area from Rotation

arc length of a curve

Measuring Curved Paths with Calculus

Measuring curved paths with calculus is important in engineering projects. Roller coaster tracks, cables, and railway lines often follow smooth curves instead of straight lines. Accurate path length helps with planning and design. A curve is first split into small segments. Each short segment is treated as a straight line between two nearby points on the curve. Adding these line segments gives an estimate of the total distance along the path. The estimate becomes better when the segments are...

arc length of a curve: problem solving

Catenary Cable Length in Power Lines

Catenary cable length helps engineers measure the full span of a hanging power line. A high-voltage line stretches 40 meters between two transmission towers and sags 10 meters because of gravity and thermal expansion. The cable forms a catenary, which is the curve of a uniform, flexible cable under its own weight. A catenary is not the same as a parabola. It is described by the hyperbolic cosine function, which gives a more accurate shape for a suspended cable. In this setup, engineers use the...

arc length function

Measuring Distance Along a Curve

The arc length function measures the distance traveled along a smooth curve from a fixed starting point to a moving endpoint. It is useful when a straight-line estimate is not accurate enough. For curves that are continuous and differentiable, arc length gives a precise way to track length along the curve. To find this distance, the curve is broken into many small pieces. Each piece is treated like a short straight line. Its length depends on the horizontal change and the vertical change over...

area of a surface of revolution

Surfaces of revolution are created when a two-dimensional curve is rotated around an axis. The rotation produces a three-dimensional shape. In engineering, this calculation can help determine the surface area of a rocket nozzle. That information matters when a heat-resistant coating must be applied evenly. When a curve is revolved about the x-axis, it sweeps out a continuous surface. To find its area, the curve is first broken into small straight-line pieces over short intervals. Each rotated...

applications of integration to find hydrostatic pressure

applications-of-integration-to-find-hydrostatic-pressure

Hydrostatic Force on Dam Walls with Integration

Hydrostatic force is the total force a fluid at rest exerts on a surface. For a horizontal surface at a fixed depth, the pressure is constant. It is found by multiplying fluid density, gravitational acceleration, and depth. A vertical dam wall is different because pressure increases with depth. The water above each point adds to the pressure below it. That means the force is not spread evenly across the wall. Integration helps measure this changing force. Pressure in a still fluid rises...

applications of integration to find centers of mass

applications-of-integration-to-find-centers-of-mass

Center of Mass in Discrete and Continuous Systems

Center of mass can be found from rotational equilibrium and from integration. A balanced plank on a pivot shows the idea clearly. When the net torque about the pivot is zero, the system is in balance. Torque is the force on an object times its perpendicular distance from the pivot. At that point, the pivot lies at the center of mass. For a set of discrete point masses, the center of mass is the position where the masses balance by weight. Each mass contributes its mass times its position,...

theorem of pappus

Pappus Theorem for Volume and Surface Area

Pappus Theorem connects centroid motion to the volume and surface area of solids of revolution. It is also called the Pappus–Guldinus Theorem. The method uses geometry to find these values when a plane region or a plane curve is rotated about an external axis. The theorem has two related parts. The first part gives the volume of a solid formed by rotating a plane region around an axis outside the region. In this case, the volume equals the area of the region multiplied by the distance traveled...

applications of integration to find consumer surplus

applications-of-integration-to-find-consumer-surplus

Consumer Surplus from Demand and Integration

Consumer surplus measures the economic gain buyers receive when they pay less than the highest price they are willing to pay. In microeconomics, this idea comes from the demand function, which links quantity to the price consumers will pay. Because willingness to pay usually falls as quantity rises, the demand curve slopes downward. When a product is sold at a fixed price, some buyers would have paid more for the first units they bought. The difference between that willingness to pay and the...

applications of integration to find blood flow

applications-of-integration-to-find-blood-flow

Using Integration to Model Blood Flow

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introduction to normal distributions

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Normal distribution helps explain how standardized test scores can be spread across a group. It is a key idea in statistics for describing symmetry, center, and variability in large sets of data. Test score data often start as a histogram. In a histogram, each bar shows how many scores fall within a score range. To turn that count-based graph into a continuous probability model, the histogram is normalized by dividing each bar height by the total number of observations and by the bin width. <br...

applications of integration to probability density functions

applications-of-integration-to-probability-density-functions

Finding Probability with Area Under a PDF

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key terms and concepts

Learn how rotating a curve around the x-axis creates a surface and how conical bands lead to a definite integral for exact surface area.

Calculating Surface Area from Rotation | 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

Calculating Surface Area from Rotation

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