Chapter 6: Problem 118
For the following exercises, determine whether the vector field is conservative and, if so, find a potential function. $$ \mathbf{F}(x, y)=\left(2 x y e^{x^{2} y}\right) \mathbf{i}+6\left(x^{2} e^{x^{2} y}\right) \mathbf{j} $$
Short Answer
Expert verified
The vector field is not conservative.
Step by step solution
01
Determine Conditions for Conservativeness
A vector field \( \mathbf{F}(x, y) = P(x, y) \mathbf{i} + Q(x, y) \mathbf{j} \) is conservative if there exists a scalar function \( f(x, y) \) such that \( abla f = \mathbf{F} \). For this, partial derivatives should satisfy \( \frac{\partial P}{\partial y} = \frac{\partial Q}{\partial x} \). Here, \( P(x, y) = 2xy e^{x^2 y} \) and \( Q(x, y) = 6x^2 e^{x^2 y} \).
02
Compute Partial Derivatives
Compute \( \frac{\partial P}{\partial y} \):\[ \frac{\partial}{\partial y} (2xy e^{x^2 y}) = 2x \frac{\partial}{\partial y}(y e^{x^2 y}) = 2x(1 + x^2 y) e^{x^2 y} = 2x e^{x^2 y} + 2x^3 y e^{x^2 y} \].Compute \( \frac{\partial Q}{\partial x} \):\[ \frac{\partial}{\partial x} (6x^2 e^{x^2 y}) = 12x e^{x^2 y} + 6x^2(2xy) e^{x^2 y} = 12xe^{x^2 y} + 12x^3 y e^{x^2 y} \].
03
Compare Partial Derivatives
Analyze the equality \( \frac{\partial P}{\partial y} = 2x e^{x^2 y} + 2x^3 y e^{x^2 y} \) and \( \frac{\partial Q}{\partial x} = 12xe^{x^2 y} + 12x^3 y e^{x^2 y} \). As we can see, they are not equal because the coefficients do not match. Specifically, \( 2x eq 12x \) and \( 2x^3 eq 12x^3 \).
04
Conclusion on Conservativeness
Since \( \frac{\partial P}{\partial y} eq \frac{\partial Q}{\partial x} \), the vector field \( \mathbf{F}(x, y) \) is not conservative.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Potential Functions
A potential function is a scalar function that can define a vector field. It is important in determining if a vector field is conservative. If a vector field \(\mathbf{F}\) has a potential function \(f(x, y)\), then \(abla f = \mathbf{F}\). This means the gradient of the potential function equals the vector field. This aligns with the idea that you can recover the original vector field from its potential function.
- If you can find a potential function, the vector field is termed conservative.
- Not all vector fields have potential functions.
Partial Derivatives
Partial derivatives are a cornerstone in understanding and finding potential functions. They let you measure how a multivariable function changes when you change one variable, while keeping others constant. In vector calculus, they are essential:
- Matches Needed: For a vector field to be conservative, the partial derivative of one component with respect to a variable should equal the partial derivative of the other component with the alternate variable. That means \(\frac{\partial P}{\partial y} = \frac{\partial Q}{\partial x}\).
- Tool for Verification: This condition comes in handy to verify if there's any potential function available for a given vector field.
- Using product rule and chain rule in calculus.
- Rigor and precision in differentiation, especially for complex functions.
Vector Calculus
Vector Calculus is the mathematics of multi-variable functions. It explores vectors and can describe motion, forces, and vector fields in physics. One of its key applications is determining if a vector field is conservative.
- Vector fields: Represented as \(\mathbf{F}(x, y, z)\), showing vector quantities changing across space.
- Conservative Vector Fields: If a vector field is conservative, it can be reduced to the gradient of some potential function \( f(x,y,z) \).
- Gradients \(abla f\), consisting of partial derivatives.
- Curl \(abla \times \mathbf{F}\), which must be zero for two-dimensional conservative fields.