Surface integrals of vectors: Need check of my work- answer doesn't look right

In summary, the task is to find the surface integral of vector field F=<x,y,x+y> over the surface z=x^2+y^2 where x^2+y^2<1, using outward pointing normals. The solution involves parametrizing the surface in polar coordinates, taking partial derivatives, finding the normal vector, and computing the dot product with F. The final answer is pi.
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Homework Statement


Find surface integral of vector field F=<x,y,x+y> over the surface z=x^2+y^2 where x^2+y^2 less than 1. Use outward pointing normals


Homework Equations





The Attempt at a Solution


So I did the whole thing and got a zero which doesn't look right to me. My algebra seems right so can you please validate the approach? Thanks:
I parametrize the surface in polar coordinates: x=r cos(theta) and y = r sin (theta). So my surface is (rcos(theta), rsin(theta), r^2).
I take partial derivatives of r and theta, find the determinant and my normal to the surface is < 2r^2cos(theta), 2r^2sin(theta), -r >
then F in terms of r and theta = < rcos(theta), rsin(theta), r(cos(theta)+sin(theta))>
dot product that with the normal to get (2r^3-r^2)(cos(theta)+sin(theta)) and integrate that for r= 0 to 1 and theta= 0 to 2pi
 
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  • #2
Never mind- it was a calculation error... Answer is pi.
 

Related to Surface integrals of vectors: Need check of my work- answer doesn't look right

1. What is a surface integral of a vector?

A surface integral of a vector is a mathematical operation that calculates the flux (flow) of a vector field through a surface. It takes into account both the magnitude and direction of the vector field.

2. What is the purpose of calculating surface integrals of vectors?

Surface integrals of vectors are useful in many areas of science, including physics and engineering. They can be used to analyze fluid flow, electromagnetism, and other physical phenomena.

3. How do you calculate a surface integral of a vector?

The calculation of a surface integral of a vector involves breaking down the surface into smaller pieces, calculating the flux through each piece, and then summing up all the individual flux values to get the total flux through the entire surface.

4. What is the difference between a surface integral of a vector and a line integral of a vector?

The main difference between the two is that a surface integral considers the flux through a 2-dimensional surface, while a line integral considers the flux through a 1-dimensional curve. In other words, a surface integral takes into account the entire surface, while a line integral only considers the direction of the vector along a specific curve.

5. Are there any real-world applications of surface integrals of vectors?

Yes, surface integrals of vectors have many real-world applications. For example, they can be used to calculate the flow of air over an airplane wing, the flow of water through a pipe, or the magnetic flux through a circuit.

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