Counterclockwise Circulation vs. Clockwise Circulation

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The discussion focuses on calculating the circulation of the vector field F = (y - z)i + (z - x)j + (x + z)k around a surface defined by z = 4 - x² - y². The curl of F was computed as ∇xF = i - 2j - 2k, leading to a counterclockwise circulation of -8π. Since the problem requests the clockwise circulation, the answer is determined to be 8π, as it is the opposite sign of the counterclockwise result. Participants confirm the correctness of the calculations and the area element used in the polar coordinates. The final conclusion is that the clockwise circulation of F is indeed 8π.
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Homework Statement


[/B]
Consider F = (y - z)i + (z - x)j + (x + z)k
Find circulation of F in the clockwise direction as seen from above, around the boundary of surface S defined by

z = 4 - x2 - y2
0 ≤ z ≤ 4

Homework Equations



∫∫ ∇xFk dA

The Attempt at a Solution



∇xF = i - 2j - 2k (after solving the cross product)
The curl of F dot k = -2

0 ≤ r ≤ 2
0 ≤ θ ≤ 2π

∫∫ -2 drdθ = ∫ -4 dθ = -8π

-8π is the counterclockwise circulation of F, but since the problem asks for the clockwise direction, would the answer just be 8π (opposite sign)?
 
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Differentiate1 said:

Homework Statement


[/B]
Consider F = (y - z)i + (z - x)j + (x + z)k
Find circulation of F in the clockwise direction as seen from above, around the boundary of surface S defined by

z = 4 - x2 - y2
0 ≤ z ≤ 4

Homework Equations



∫∫ ∇xFk dA

The Attempt at a Solution



∇xF = i - 2j - 2k (after solving the cross product)
The curl of F dot k = -2

0 ≤ r ≤ 2
0 ≤ θ ≤ 2π

∫∫ -2 drdθ = ∫ -4 dθ = -8π

-8π is the counterclockwise circulation of F, but since the problem asks for the clockwise direction, would the answer just be 8π (opposite sign)?

It will be if the ##-8\pi## is correct. Is your polar element of area correct?
 
Yes, I checked and -8π is the correct counterclockwise circulation.
Thanks.
 
You should recheck the area element again, even though you accidentally got the right answer.
 
Question: A clock's minute hand has length 4 and its hour hand has length 3. What is the distance between the tips at the moment when it is increasing most rapidly?(Putnam Exam Question) Answer: Making assumption that both the hands moves at constant angular velocities, the answer is ## \sqrt{7} .## But don't you think this assumption is somewhat doubtful and wrong?

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