Not sure if this surface integral is right

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The discussion revolves around a surface integral problem where the initial manual integration yielded an incorrect result of 5/6. The user identified errors in their face-by-face method, particularly with the outward direction of the normal on the first and third faces, and mistakes in the integration of the second face. After addressing these issues, the user successfully recalculated the integral and arrived at the correct answer of 1/4. This highlights the importance of correctly determining the orientation of normals and carefully checking each step in the integration process. The final resolution confirms the correct approach to solving the surface integral.
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Homework Statement


16jqcw.png


The Attempt at a Solution



I did the manual integration of part (i) and got an answer of 5/6 instead, I'm not sure which part is wrong.. For the surfaces, I start off with the surface in the x-z plane, then the slanted plane, then the y-z plane, then the top of the prism and finally the bottom of the prism.

For the slanted plane, I projected it onto the x-z plane to do the integration..

Part (a)
2dtngx0.png

k2beox.png
 
Last edited:
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I see two errors in the face by face method.
You have the sign of the normal wrong in the first and third faces. The direction is always outwards.
For the second face, you correctly had ∫xy2+x2, but went wrong in the next line.
 
haruspex said:
I see two errors in the face by face method.
You have the sign of the normal wrong in the first and third faces. The direction is always outwards.
For the second face, you correctly had ∫xy2+x2, but went wrong in the next line.

Thanks! I will try again.
 
haruspex said:
I see two errors in the face by face method.
You have the sign of the normal wrong in the first and third faces. The direction is always outwards.
For the second face, you correctly had ∫xy2+x2, but went wrong in the next line.

Finally got the answer as 1/4 ! Thanks alot!
 
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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