Math Problem Statement

Determine whether the vector field F(x, y) is conservative. If it is, find a potential function for the vector field. (If an answer does not exist, enter DNE.)

Solution

To determine whether the vector field F(x,y)=8yxi+8x2y2j\mathbf{F}(x, y) = \frac{8y}{x} \mathbf{i} + \frac{8x^2}{y^2} \mathbf{j} is conservative, we follow these steps:


Step 1: Check if the vector field is conservative.

A vector field is conservative if the curl of the field is zero (in two dimensions, this simplifies to checking if Qx=Py\frac{\partial Q}{\partial x} = \frac{\partial P}{\partial y}, where:

  • P(x,y)=8yxP(x, y) = \frac{8y}{x} (the component of i\mathbf{i}),
  • Q(x,y)=8x2y2Q(x, y) = \frac{8x^2}{y^2} (the component of j\mathbf{j}).

Calculate Qx\frac{\partial Q}{\partial x}:

Q(x,y)=8x2y2    Qx=x(8x2y2)=16xy2.Q(x, y) = \frac{8x^2}{y^2} \implies \frac{\partial Q}{\partial x} = \frac{\partial}{\partial x} \left( \frac{8x^2}{y^2} \right) = \frac{16x}{y^2}.

Calculate Py\frac{\partial P}{\partial y}:

P(x,y)=8yx    Py=y(8yx)=8x.P(x, y) = \frac{8y}{x} \implies \frac{\partial P}{\partial y} = \frac{\partial}{\partial y} \left( \frac{8y}{x} \right) = \frac{8}{x}.


Compare Qx\frac{\partial Q}{\partial x} and Py\frac{\partial P}{\partial y}:

Qx=16xy2,Py=8x.\frac{\partial Q}{\partial x} = \frac{16x}{y^2}, \quad \frac{\partial P}{\partial y} = \frac{8}{x}.

Since QxPy\frac{\partial Q}{\partial x} \neq \frac{\partial P}{\partial y}, the vector field is not conservative.


Final Answer:

  • The vector field is not conservative.
  • Therefore, a potential function does not exist.

Do you have further questions or need clarifications? Here are five related questions:

  1. How do you compute the curl of a 2D vector field in general?
  2. Why does a zero curl imply that a field is conservative?
  3. Can a field be conservative in some region but not in others?
  4. What are the physical interpretations of conservative vector fields?
  5. How would you verify if a 3D vector field is conservative?

Tip: Always ensure the domain of the vector field is connected and excludes singularities when checking for conservativeness.

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Math Problem Analysis

Mathematical Concepts

Vector Fields
Conservative Fields
Partial Derivatives

Formulas

Conservative field check: ∂Q/∂x = ∂P/∂y
Potential function derivation for F(x, y)

Theorems

Fundamental Theorem for Conservative Vector Fields

Suitable Grade Level

College-level Mathematics