Math Problem Statement

F(x,y) = <x^2, y^2> along a path from (0,0) to (1,1). Find the integral of F * dr using a parabolic path

Solution

To evaluate the line integral of the vector field F(x,y)=x2,y2\mathbf{F}(x, y) = \langle x^2, y^2 \rangle along a parabolic path from (0,0)(0, 0) to (1,1)(1, 1), let’s proceed step by step.


1. Represent the Path

We need a parabolic path. A common choice is: y=x2y = x^2 with xx varying from 00 to 11. Therefore, the path can be parameterized as: r(t)=t,t2,t[0,1].\mathbf{r}(t) = \langle t, t^2 \rangle, \quad t \in [0, 1].

The differential of r(t)\mathbf{r}(t) is: r(t)=ddtt,t2=1,2t,\mathbf{r}'(t) = \frac{d}{dt} \langle t, t^2 \rangle = \langle 1, 2t \rangle, and thus: dr=r(t)dt=1,2tdt.d\mathbf{r} = \mathbf{r}'(t) \, dt = \langle 1, 2t \rangle \, dt.


2. Write the Line Integral

The line integral is defined as: CFdr,\int_C \mathbf{F} \cdot d\mathbf{r}, where F=x2,y2\mathbf{F} = \langle x^2, y^2 \rangle. Substituting the parameterization (x,y)=(t,t2)(x, y) = (t, t^2): F(t)=t2,(t2)2=t2,t4.\mathbf{F}(t) = \langle t^2, (t^2)^2 \rangle = \langle t^2, t^4 \rangle.

Thus, the dot product Fdr\mathbf{F} \cdot d\mathbf{r} becomes: Fdr=t2,t41,2t=t2(1)+t4(2t)=t2+2t5.\mathbf{F} \cdot d\mathbf{r} = \langle t^2, t^4 \rangle \cdot \langle 1, 2t \rangle = t^2(1) + t^4(2t) = t^2 + 2t^5.


3. Evaluate the Integral

Now, integrate t2+2t5t^2 + 2t^5 over t[0,1]t \in [0, 1]: 01(t2+2t5)dt=01t2dt+012t5dt.\int_0^1 (t^2 + 2t^5) \, dt = \int_0^1 t^2 \, dt + \int_0^1 2t^5 \, dt.

For the first term: 01t2dt=[t33]01=133033=13.\int_0^1 t^2 \, dt = \left[\frac{t^3}{3}\right]_0^1 = \frac{1^3}{3} - \frac{0^3}{3} = \frac{1}{3}.

For the second term: 012t5dt=201t5dt=2[t66]01=2(166066)=26=13.\int_0^1 2t^5 \, dt = 2 \int_0^1 t^5 \, dt = 2 \left[\frac{t^6}{6}\right]_0^1 = 2 \left(\frac{1^6}{6} - \frac{0^6}{6}\right) = \frac{2}{6} = \frac{1}{3}.

Add the two results: 01(t2+2t5)dt=13+13=23.\int_0^1 (t^2 + 2t^5) \, dt = \frac{1}{3} + \frac{1}{3} = \frac{2}{3}.


Final Answer:

The value of the line integral is: 23\boxed{\frac{2}{3}}


Do you want detailed steps for each parameterization, or have any related questions? Here are 5 follow-up questions to deepen your understanding:

  1. How does the choice of path affect the line integral in vector fields?
  2. Can you explain the geometric meaning of the line integral in this context?
  3. What happens if you use a different parabolic path, such as y=x3y = x^3?
  4. How would the integral change if F(x,y)\mathbf{F}(x, y) had an additional term, like x2,y2+x\langle x^2, y^2 + x \rangle?
  5. What is the relationship between this integral and the concept of work done in physics?

Tip: Always ensure your parameterization matches the given path before computing line integrals!

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Math Problem Analysis

Mathematical Concepts

Vector Fields
Line Integrals
Parametric Equations

Formulas

Line integral formula: ∫C F · dr
Parametric representation of a curve: r(t) = <x(t), y(t)>
Dot product formula: <a, b> · <c, d> = ac + bd

Theorems

Line Integral Theorem for vector fields
Basic Integration techniques

Suitable Grade Level

Undergraduate (Calculus II or III)