Find the flux of this vector field

In summary, The problem at hand is finding the flux of a vector field through a given plan with z values ranging from 0 to 1. The surface given is the upper nappe of a cone, with good parametric equations being x= r cos(\theta), y= r sin(\theta), and z= r. The vector equation would be \vec{r}(r, \theta)= r cos(\theta)\vec{i}+ r sin(\theta)\vec{j}+ r \vec{k}. The limits for r are 0 to 1, and for theta 0 to 2\pi. It is recommended to do the integrations with respect to theta first to avoid getting 0 as a result.
  • #1
asi123
258
0

Homework Statement



I need to find the flux of this vector field (in the pic) that goes through this plan (in the pic) and z goes from 0 to 1.
How am I suppose to do that?


Homework Equations





The Attempt at a Solution

 

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  • #2
The surface is [itex]z= \sqrt{x^2+ y^2}[/itex], the upper nappe of a cone. In cylindrical coordinates, that is z= r. So good parametic equations would be [itex]x= r cos(\theta)[/itex], [itex]y= r sin(\theta)[/itex], [itex]z= r[/itex] which means that the vector equation would be
[itex]\vec{r}(r, \theta)= r cos(\theta)\vec{i}+ r sin(\theta)\vec{j}+ r \vec{k}[/itex]. Since z goes from 0 to 1, r goes from 0 to 1 and [itex]theta[/itex], of course, from 0 to [itex]2\pi[/itex].

Does that help?
 
  • #3
HallsofIvy said:
The surface is [itex]z= \sqrt{x^2+ y^2}[/itex], the upper nappe of a cone. In cylindrical coordinates, that is z= r. So good parametic equations would be [itex]x= r cos(\theta)[/itex], [itex]y= r sin(\theta)[/itex], [itex]z= r[/itex] which means that the vector equation would be
[itex]\vec{r}(r, \theta)= r cos(\theta)\vec{i}+ r sin(\theta)\vec{j}+ r \vec{k}[/itex]. Since z goes from 0 to 1, r goes from 0 to 1 and [itex]theta[/itex], of course, from 0 to [itex]2\pi[/itex].

Does that help?

Check this out, is that what you meant?
 

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  • #4
Once you have done the cross product, and the integral, yes, that should be correct. I would recommend you do the integrations with respect to [itex]\theta[/itex] first. Most of those trig functions, integrated from 0 to [itex]2\pi[/itex] will give 0.
 
  • #5
HallsofIvy said:
Once you have done the cross product, and the integral, yes, that should be correct. I would recommend you do the integrations with respect to [itex]\theta[/itex] first. Most of those trig functions, integrated from 0 to [itex]2\pi[/itex] will give 0.

10x a lot.
 
  • #6
asi123 said:
10x a lot.

10-4 good buddy!
 

What is a vector field?

A vector field is a mathematical function that assigns a vector to every point in a given space. It is used to describe the direction and magnitude of a physical quantity, such as velocity or force, at each point in space.

What is flux?

Flux is a measure of the flow of a vector field across a given surface. It represents the amount of the vector field passing through the surface per unit area.

How do you find the flux of a vector field?

The flux of a vector field can be found by taking the dot product of the vector field and the normal vector to the surface, and then integrating over the surface. This can be represented mathematically as ∫∫S F⋅dS, where F is the vector field and dS is the differential surface area element.

What is the significance of finding the flux of a vector field?

Finding the flux of a vector field is important in many areas of science and engineering, such as fluid dynamics, electromagnetism, and heat transfer. It allows us to understand the flow of a physical quantity through a given surface, and can help us make predictions and solve problems in various fields.

What are some real-world applications of finding the flux of a vector field?

Some examples of real-world applications include calculating the air flow through a ventilation system, determining the rate of heat transfer in a building, and analyzing the flow of water in a river or ocean. It is also used in various engineering and scientific simulations, such as weather forecasting and flight simulations.

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