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Section 11.4 Assignment 4

  1. Construct a parametric description of a lampshade and describe the orientation you've chosen. (You can choose the shape of the lampshade within reason.) (6)

  2. Construct a parametric description of a truncated sphere and describe the orientation you've chosen. (You can choose how much of the sphere to truncate.) (6)

  3. Calculate the flux of the field \(F = (x, y, x^2 + y^2)\) over the surface \(z = x^2 + y^2\) for \(z \in [0,5]\text{.}\) The surface has an outward facing normal and is open at the top. (5)

  4. Calculate the flux of the field \(F = \left( \cos z + z \cos x, \sin x, \frac{z^2}{2} \sin x \right)\) over the sphere of radius 1 centred at \((3,-2,-1)\text{.}\) The sphere has outward facing normal. (5)

  5. Calculate the flux of the field \(F = (x^2, y-z, y+z)\) over the boundary of the tetrahedron with vertics \((0,0,0)\text{,}\) \((2,0,0)\text{,}\) \((0,2,0)\) and \((0,0,2))\text{.}\) The surface of the tetrahedron has an outward facing normal. (5)

  6. Calculate the flux of the field \(F = (8z - 8y, 6x, -4y)\) over the portion of the plane \(3x - y - z = 4\) which lies above/below the interval \([0,1]\times[0,3]\)in the \(xy\) plane. The normal points above the plane (so it has a positive \(z\) component). (5)

  7. Calculate the flux of the field \(F = \left( \frac{1}{y^2 + z^2}, \frac{1}{x^2 + z^2}, \frac{1}{x^2 + y^2} \right) \) over the infinite cone \(z = 4 \sqrt{x^2 + y^2}\) for \(z \in (0, \infty)\text{.}\) The cone has an outward facing normal. (5)

  8. Calculate the flux of the field \(F = (3, 2y^2, x)\) over the open cylinder \(x^2 + z^2 = 4\) with \(y \in [3,7]\text{.}\) The cylinder has an outward facing normal. (5)

  9. Calculate the flux of the field \(F = (2xy, x^2 + 2yz, -2yz - z^2) \) over the entire \(xy\) plane. The normal to the plane points in the positive \(z\) direction. (5)

  10. Let \(f\) be a scalar field, \(F\) be a vector field, and \(\sigma\) be a parametric surface. Prove this identity. (3)

    \begin{equation*} \int_{\del \sigma} (fF) \cdot ds = \int_{\sigma} \left( (\nabla f \times F) + f (\nabla \times F) \right) \cdot dA \end{equation*}
  11. Let \(F\) be a vector field of the form \(F = \left( F_1(y,z), F_2(x,z), F_3(x,y) \right)\text{.}\) Prove that the flux of \(F\) over any closed surface is 0. (3)