Worksheet: Green’s Theorem

In this worksheet, we will practice applying Green’s theorem to evaluate a line integral around a closed curve as the double integral over the plane region bounded by the curve.

Q1:

Use Green’s theorem to determine the conditions on π‘Ž, 𝑏, 𝑐, and 𝑑 for the vector field F(π‘₯,𝑦)=βŸ¨π‘Žπ‘₯+𝑏𝑦,𝑐π‘₯+π‘‘π‘¦βŸ© to be conservative. In that case, what is the potential function 𝑓(π‘₯,𝑦) for F that satisfies 𝑓(0,0)=0?

  • A𝑐=βˆ’π‘,𝑓(π‘₯,𝑦)=π‘Ž2π‘₯βˆ’π‘π‘₯𝑦+𝑑2π‘¦οŠ¨οŠ¨
  • B𝑐=βˆ’π‘,𝑓(π‘₯,𝑦)=π‘Ž2π‘₯βˆ’2𝑏π‘₯𝑦+𝑑2π‘¦οŠ¨οŠ¨
  • C𝑐=𝑏,𝑓(π‘₯,𝑦)=π‘Žπ‘₯+𝑏π‘₯𝑦+π‘‘π‘¦οŠ¨οŠ¨
  • D𝑐=𝑏,𝑓(π‘₯,𝑦)=π‘Ž2π‘₯+𝑏π‘₯𝑦+𝑑2π‘¦οŠ¨οŠ¨
  • E𝑐=𝑏,𝑓(π‘₯,𝑦)=π‘Ž2π‘₯+2𝑏π‘₯𝑦+𝑑2π‘¦οŠ¨οŠ¨

Q2:

Use Green’s theorem to find ο„Έβ‹…οŒ’Frd, where 𝐢 is the circle of radius π‘Ÿ and center at the origin and F(π‘₯,𝑦)=⟨2π‘₯+5𝑦,2π‘₯+7π‘¦βŸ©.

  • Aβˆ’2πœ‹π‘ŸοŠ¨
  • B5πœ‹π‘ŸοŠ¨
  • C3πœ‹π‘ŸοŠ¨
  • Dβˆ’5πœ‹π‘ŸοŠ¨
  • Eβˆ’3πœ‹π‘ŸοŠ¨

Q3:

The figure shows the graph of 𝑓(π‘₯)=βˆ’3ο€Όπ‘₯+13(π‘₯βˆ’1) over the interval [0,1]. Let 𝑅 be the shaded region and 𝐢 its boundary, traced counterclockwise. Let Fij(π‘₯,𝑦)=𝑦+𝑦.

Use Green’s theorem to calculate ο…‡β‹…οŒ’Frd.

Calculate ο„Έβ‹…οŒ’οŽ Frd, where 𝐢 is the line from π‘Ž to 𝑏.

Calculate ο„Έβ‹…οŒ’οŽ‘Frd, where 𝐢 is the curve from 𝑏 to 𝑐.

Calculate ο„Έβ‹…οŒ’οŽ’Frd, where 𝐢 is the line from 𝑐 to π‘Ž.

Q4:

The figure shows the steps to producing a curve 𝐢. It starts as the boundary of the unit square in Figure (a). In Figure (b), we remove a square quarter of the area of the square in (a). In Figure (c), we add a square quarter of the area that we removed in (b). In Figure (d), we remove a square quarter of the area of the square we added in (c). If we continue to do this indefinitely, we will get the curve 𝐢. We let 𝑅 be the region enclosed by 𝐢.

By summing a suitable series, find the area of region 𝑅. Give your answer as a fraction.

  • A14
  • B45
  • C12
  • D23
  • E34

Consider the vector field F(π‘₯,𝑦)=βŸ¨π‘¦,2π‘₯⟩. What is the function πœ•πœ•π‘₯βˆ’πœ•πœ•π‘¦FF?

Use Green’s theorem to evaluate the line integral ο„Έβ‹…οŒ’Fr(d), where 𝐢 is the curve above.

  • A45
  • B14
  • C34
  • D85
  • E15

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