Chapter 14: Problem 10
Discuss one of the parallels between a conservative vector field and a source- free vector field.
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Chapter 14: Problem 10
Discuss one of the parallels between a conservative vector field and a source- free vector field.
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Prove the following identities. Assume that \(\varphi\) is \(a\) differentiable scalar-valued function and \(\mathbf{F}\) and \(\mathbf{G}\) are differentiable vector fields, all defined on a region of \(\mathbb{R}^{3}\). $$\nabla(\mathbf{F} \cdot \mathbf{G})=(\mathbf{G} \cdot \nabla) \mathbf{F}+(\mathbf{F} \cdot \nabla) \mathbf{G}+\mathbf{G} \times(\nabla \times \mathbf{F})+\mathbf{F} \times(\nabla \times \mathbf{G})$$
If two functions of one variable, \(f\) and \(g\), have the property that \(f^{\prime}=g^{\prime},\) then \(f\) and \(g\) differ by a constant. Prove or disprove: If \(\mathbf{F}\) and \(\mathbf{G}\) are nonconstant vector fields in \(\mathbb{R}^{2}\) with curl \(\mathbf{F}=\operatorname{curl} \mathbf{G}\) and \(\operatorname{div} \mathbf{F}=\operatorname{div} \mathbf{G}\) at all points of \(\mathbb{R}^{2},\) then \(\mathbf{F}\) and \(\mathbf{G}\) differ by a constant vector.
Explain why or why not Determine whether the following statements are true and give an explanation or counterexample. a. A paddle wheel with its axis in the direction \langle 0,1,-1\rangle would not spin when put in the vector field $$ \mathbf{F}=\langle 1,1,2\rangle \times\langle x, y, z\rangle $$ b. Stokes' Theorem relates the flux of a vector field \(\mathbf{F}\) across a surface to the values of \(\mathbf{F}\) on the boundary of the surface. c. A vector field of the form \(\mathbf{F}=\langle a+f(x), b+g(y)\) \(c+h(z)\rangle,\) where \(a, b,\) and \(c\) are constants, has zero circulation on a closed curve. d. If a vector field has zero circulation on all simple closed smooth curves \(C\) in a region \(D,\) then \(\mathbf{F}\) is conservative on \(D\)
Prove Green's Second Identity for scalar-valued functions \(u\) and \(v\) defined on a region \(D\) : $$\iiint_{D}\left(u \nabla^{2} v-v \nabla^{2} u\right) d V=\iint_{S}(u \nabla v-v \nabla u) \cdot \mathbf{n} d S$$ (Hint: Reverse the roles of \(u\) and \(v\) in Green's First Identity.)
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 that of the gradient, which is the direction of greatest temperature decrease. The divergence of the heat flow vector is \(\nabla \cdot \mathbf{F}=-k \nabla \cdot \nabla T=-k \nabla^{2} T\) (the Laplacian of \(T\)). Compute the heat flow vector field and its divergence for the following temperature distributions. $$T(x, y, z)=100(1+\sqrt{x^{2}+y^{2}+z^{2}})$$
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