Chapter 5: Problem 5
For the following exercises, without using Stokes' theorem, calculate directly both the flux of \(\operatorname{curl} \mathbf{F} \cdot \mathbf{N}\) over the given surface and the circulation integral around its boundary, assuming all boundaries are oriented clockwise as viewed from above.\(\mathbf{F}(x, y, z)=(x+2 z) \mathbf{i}+(y-x) \mathbf{j}+(z-y) \mathbf{k} ; S\) is a triangular region with vertices \((3,0,0),(0,3 / 2,0)\), and \((0,0,3) .\)
Short Answer
Step by step solution
Define the Surface and Normal Vector
Calculate the Normal Vector
Normalize the Normal Vector
Compute the Curl of \(\mathbf{F}\)
Calculate the Flux Through the Surface
Set Up the Line Integral for Circulation
Compute the Line Integrals for Each Segment
Evaluate the Circulation Integral
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Flux of Curl
\[ \int \int_S (abla \times \mathbf{F}) \cdot \mathbf{n} \, dS \]
Here's a step-by-step breakdown of what happens:
- Calculate \(abla \times \mathbf{F}\), which involves taking the curl of the vector field. This is done using a determinant method with partial derivatives.
- Find a normal vector, \(\mathbf{n}\), to the given surface. This is usually obtained from the cross product of two vectors lying on the surface.
- Compute the surface integral, where you multiply \(abla \times \mathbf{F}\) by the unit normal vector \(\mathbf{n}\) and integrate over the whole surface.
Circulation Integral
- \(C\) denotes the closed contour or path.
- \(\mathbf{F}\) is the vector field through which the circulation is being measured.
The process involves breaking the path into segments and parameterizing each:
- For each segment, derive an expression for \(d\mathbf{r}\), the infinitesimal line element along that path.
- Calculate the dot product \(\mathbf{F} \cdot d\mathbf{r}\) across the parameter range of the path segment.
- Sum the integrals across all segments to determine the total circulation.
Surface Integral
- Determine the area of the surface \(S\).
- Find the normal projection of the vector field (often the curl in this context) onto the surface.
- Evaluate the integral over the surface using the vector normal \(\mathbf{n}\).
Line Integral
- Identify the path over which the integral is evaluated. Typically, this involves parameterization.
- Compute the dot product \(\mathbf{F} \cdot \mathbf{T}\), where \(\mathbf{T}\) is the tangent vector along the path.
- Integrate over the entire path considering your defined parameterization.
In the exercise given, the triangular path involves three linear segments, each requiring specific parameterization:
- Segment 1: Set from \((3,0,0)\) to \((0,\frac{3}{2},0)\) and parameterize the line.
- Segment 2: Progresses to \((0,0,3)\) with another distinct parameterization.
- Segment 3: Closes the triangle by returning to the starting point, necessitating a third parameterization.