Line integral across a vector field

In summary, the problem involves finding the integral of a vector field \mathbf{F} along a segment of the curve y=x^2, from (-1,1) to (1,1). To solve this, the curve is parametrized as \mathbf{r}(t)=<t,t^2> from -1 to 1, and the path is checked for independence. The resulting integrand, involving e^{\sin^4{y}}, may be difficult to solve.
  • #1
clandarkfire
31
0

Homework Statement


[tex]\int_C \mathbf F\cdot d \mathbf r[/tex] where [tex]\mathbf F = x^2\vec{i}+e^{\sin^4{y}}\vec{j}[/tex]
and C is the segment of y=x^2 from (-1,1) to (1,1).

Homework Equations


[tex]\int_C \mathbf F\cdot d \mathbf r=\int_a^b \mathbf F( \mathbf r(t))\cdot r'(t) dt=\int_C Pdx+Qdy[/tex] where [tex]\mathbf F = P\vec{i}+Q\vec{j}[/tex]

The Attempt at a Solution


I parametrize C:
[tex]\mathbf r(t)=<t,t^2>|-1\leq t \leq 1[/tex]
Well, I know how to apply the equations above as well as Green's theorem (I use this by letting C2 be a line from (1,1) to (-1,1) and integrating across the enclosed disk D), but no matter what I do, I find myself having to integrate some version of [tex]e^{\sin^4{y}}[/tex]
There has to be some trick I'm missing. Could someone point me in the right direction?
 
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  • #2
clandarkfire said:

Homework Statement


[tex]\int_C \mathbf F\cdot d \mathbf r[/tex] where [tex]\mathbf F = x^2\vec{i}+e^{\sin^4{y}}\vec{j}[/tex]
and C is the segment of y=x^2 from (-1,1) to (1,1).

Homework Equations


[tex]\int_C \mathbf F\cdot d \mathbf r=\int_a^b \mathbf F( \mathbf r(t))\cdot r'(t) dt=\int_C Pdx+Qdy[/tex] where [tex]\mathbf F = P\vec{i}+Q\vec{j}[/tex]

The Attempt at a Solution


I parametrize C:
[tex]\mathbf r(t)=<t,t^2>|-1\leq t \leq 1[/tex]
Well, I know how to apply the equations above as well as Green's theorem (I use this by letting C2 be a line from (1,1) to (-1,1) and integrating across the enclosed disk D), but no matter what I do, I find myself having to integrate some version of [tex]e^{\sin^4{y}}[/tex]
There has to be some trick I'm missing. Could someone point me in the right direction?
If [itex]\displaystyle \mathbf r(t)=<t,\,t^2>\,,\ [/itex] then [itex]\displaystyle d\mathbf r(t)=<1,\,2t>dt\ . [/itex]

You will have an odd integrand involving the problematic [itex]\displaystyle e^{\sin^4{y}}\ .[/itex]
 
Last edited:
  • #3
Does this get me anywhere? It seems to still leave me with something unsolveable.
 
  • #4
Check for independence of path and use the straight line from (-1,1) to (1,1).
 

1. What is a line integral across a vector field?

A line integral across a vector field is a mathematical concept that represents the sum of the values of a vector field along a specific path or curve. It is used to calculate the total amount of a vector quantity, such as force or displacement, along a given path.

2. How is a line integral across a vector field calculated?

To calculate a line integral across a vector field, you must first define the path or curve along which the integral is being calculated. Then, the vector field function is integrated along that path, with respect to the variable of integration. The result is a single numerical value that represents the total amount of the vector quantity along the path.

3. What is the significance of a line integral across a vector field?

A line integral across a vector field is important because it allows us to calculate the total amount of a vector quantity, such as work or flux, along a specific path. This can be useful in many real-world applications, such as calculating the amount of force needed to move an object along a certain path or determining the flow of a fluid through a given curve.

4. What are some common applications of line integrals across vector fields?

Line integrals across vector fields are used in various fields of science and engineering, such as physics, engineering, and fluid dynamics. They can be used to calculate work done by a force, flux of a vector field through a surface, and circulation of a vector field around a closed path. They are also used in the study of conservative and non-conservative vector fields.

5. How does a line integral across a vector field differ from a regular integral?

Unlike a regular integral, which is calculated over a single variable, a line integral across a vector field is calculated along a specific path or curve. This means that the value of the integral can change depending on the path chosen. Additionally, a regular integral is used to find the area under a curve, while a line integral across a vector field is used to find the total amount of a vector quantity along a path.

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