Chapter 17: Problem 9
Testing for conservative vector fields Determine whether the following vector fields are conservative (in \(\mathbb{R}^{2}\) or \(\mathbb{R}^{3}\) ). $$\mathbf{F}=\langle 1,1\rangle$$
Short Answer
Expert verified
Answer: The given vector field is conservative, as the curl of \(\mathbf{F}\) is equal to zero.
Step by step solution
01
Write down the given vector field
The vector field given in the exercise is:
$$\mathbf{F}=\langle 1,1 \rangle$$
02
Compute the partial derivatives of the components
Compute the partial derivatives of the component functions of \(\mathbf{F}\) with respect to \(x\) and \(y\):
$$\frac{\partial F_1}{\partial x} = \frac{\partial}{\partial x}(1) = 0$$
$$\frac{\partial F_2}{\partial y} = \frac{\partial}{\partial y}(1) = 0$$
03
Evaluate the curl
Compute the 2-dimensional curl:
$$\text{curl}(\mathbf{F})=\frac{\partial F_2}{\partial x} - \frac{\partial F_1}{\partial y}$$
Substitute the calculated partial derivatives in the curl expression:
$$\text{curl}(\mathbf{F}) = 0 - 0 = 0$$
04
Test for conservative vector field
Since the curl of \(\mathbf{F}\) is equal to zero, the given vector field is conservative.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
vector field
A vector field, such as the one in this exercise, is a function that assigns a vector to each point in a space. In simple terms, you can think of a vector field as a collection of arrows spread across a graph, where each arrow has a specific direction and magnitude. These arrows represent how a vector quantity, like force or velocity, varies over space. The given vector field is expressed as:\[\mathbf{F} = \langle 1,1 \rangle\]Here, the vector \(\langle 1, 1 \rangle\) indicates that at any point in the space, the vector points equally in the direction of both \(x\) and \(y\) axes with a magnitude of 1 for each direction. This might appear trivial because it doesn't change with different \(x\) or \(y\), indicating a constant vector field. In vector calculus, determining properties like constant behavior is crucial in further analyses, like finding if a field is conservative.
partial derivatives
Partial derivatives are fundamental in dealing with functions of multiple variables, like our vector field components. When we're given vectors in two-dimensional space, the functions (components of the vector) can depend on both \(x\) and \(y\) variables.To compute the partial derivative, we hold one variable at a time constant while differentiating with respect to the other. For our vector field \(\mathbf{F} = \langle 1, 1 \rangle\), the components are constant (\(1\)). This simplifies the computation:- \(\frac{\partial F_1}{\partial x} = \frac{\partial}{\partial x}(1) = 0\)- \(\frac{\partial F_2}{\partial y} = \frac{\partial}{\partial y}(1) = 0\)These calculations reveal that the components don't change with respect to \(x\) and \(y\), confirming the constant nature of the vector field.
curl
The curl of a vector field measures its tendency to rotate around a point. It is a vector operation that shows how the field twists or swirls in a two- or three-dimensional space. For a vector field in two dimensions like \( \mathbf{F} \), the curl is computed as:\[\text{curl}(\mathbf{F}) = \frac{\partial F_2}{\partial x} - \frac{\partial F_1}{\partial y}\]Here, we specifically look at the rate of change difference between the \(x\)-component of one part and the \(y\)-component of another part of the vector. In our case, both partial derivatives are zero:- \(\text{curl}(\mathbf{F}) = 0 - 0 = 0\)Achieving a zero result for the curl in the context of a 2D vector field implies no rotational component, a crucial consideration in categorizing the field's nature.
\nabla \times F = 0 (curl zero)
When studying vector fields, a field is deemed conservative if the curl is zero. Mathematically, this is expressed as \( abla \times \mathbf{F} = 0 \). This condition implies that there are no local rotations; in simpler terms, the field has no tendency to spin or circulate around points in space.For \( \mathbf{F} = \langle 1, 1 \rangle \), we confirmed the curl is zero, indicating that the field is conservative. Such fields have significant properties:- A conservative field can be expressed as the gradient of some scalar potential function.- Path independence: the work done by moving along a path in the vector field depends only on the starting and ending points, not the specific path taken.Understanding that \( abla \times \mathbf{F} = 0 \) exemplifies why identifying a field as conservative helps simplify many physical and mathematical problems.