Chapter 17: Problem 17
Sketch the following vector fields. $$\mathbf{F}=\langle x, y-x\rangle$$
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Chapter 17: Problem 17
Sketch the following vector fields. $$\mathbf{F}=\langle x, y-x\rangle$$
These are the key concepts you need to understand to accurately answer the question.
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Choosing a more convenient surface The goal is to evaluate \(A=\iint_{S}(\nabla \times \mathbf{F}) \cdot \mathbf{n} d S,\) where \(\mathbf{F}=\langle y z,-x z, x y\rangle\) and \(S\) is the surface of the upper half of the ellipsoid \(x^{2}+y^{2}+8 z^{2}=1\) \((z \geq 0)\) a. Evaluate a surface integral over a more convenient surface to find the value of \(A\) b. Evaluate \(A\) using a line integral.
Miscellaneous surface integrals Evaluate the following integrals using the method of your choice. Assume normal vectors point either outward or upward. $$\begin{aligned} &\iint_{S} \nabla \ln |\mathbf{r}| \cdot \mathbf{n} d S, \text { where } S \text { is the hemisphere } x^{2}+y^{2}+z^{2}=a^{2}\\\ &\text { for } z \geq 0, \text { and where } \mathbf{r}=\langle x, y, z\rangle \end{aligned}$$
Suppose a solid object in \(\mathbb{R}^{3}\) has a temperature distribution given by \(T(x, y, z) .\) The heat flow vector field in the object is \(\mathbf{F}=-k \nabla T,\) where the conductivity \(k>0\) is a property of the material. Note that the heat flow vector points in the direction opposite to that of the gradient, which is the direction of greatest temperature decrease. The divergence of the heat flow vector is \(\nabla \cdot \mathbf{F}=-k \nabla \cdot \nabla T=-k \nabla^{2} T(\text {the Laplacian of } T) .\) Compute the heat flow vector field and its divergence for the following temperature distributions. $$T(x, y, z)=100 e^{-x^{2}+y^{2}+z^{2}}$$
Surface integrals of vector fields Find the flux of the following vector fields across the given surface with the specified orientation. You may use either an explicit or a parametric description of the surface. \(\mathbf{F}=\langle-y, x, 1\rangle\) across the cylinder \(y=x^{2},\) for \(0 \leq x \leq 1\) \(0 \leq z \leq 4 ;\) normal vectors point in the general direction of the positive y-axis.
Surface area of a torus a. Show that a torus with radii \(R > r\) (see figure) may be described parametrically by \(\mathbf{r}(u, v)=\langle(R+r \cos u) \cos v\) \((R+r \cos u) \sin v, r \sin u\rangle,\) for \(0 \leq u \leq 2 \pi, 0 \leq v \leq 2 \pi\) b. Show that the surface area of the torus is \(4 \pi^{2} R r\)
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