Chapter 9: Problem 1
Find curl \(\mathbf{v}\) for \(\mathbf{v}\) given with respect to right-handed Cartesian coordinates. Show the details of your work. $$\left[\begin{array}{lll}y, & 2 x^{2}, & 0\end{array}\right]$$
Short Answer
Expert verified
The curl of the vector field is \( \langle 0, 0, 4x - 1 \rangle \).
Step by step solution
01
Understand the Curl Formula
To find the curl of a vector field \( \mathbf{v} = \langle P, Q, R \rangle \), we use the formula: \( abla \times \mathbf{v} = \left( \frac{\partial R}{\partial y} - \frac{\partial Q}{\partial z}, \frac{\partial P}{\partial z} - \frac{\partial R}{\partial x}, \frac{\partial Q}{\partial x} - \frac{\partial P}{\partial y} \right) \).
02
Identify Components of \(\mathbf{v}\)
From the given vector field \( \mathbf{v} = \langle y, 2x^2, 0 \rangle \), identify the components: \( P = y \), \( Q = 2x^2 \), and \( R = 0 \).
03
Compute \( \frac{\partial R}{\partial y} \) and \( \frac{\partial Q}{\partial z} \)
Calculate \( \frac{\partial R}{\partial y} = \frac{\partial}{\partial y}(0) = 0 \) and \( \frac{\partial Q}{\partial z} = \frac{\partial}{\partial z}(2x^2) = 0 \).
04
Compute \( \frac{\partial P}{\partial z} \) and \( \frac{\partial R}{\partial x} \)
Calculate \( \frac{\partial P}{\partial z} = \frac{\partial}{\partial z}(y) = 0 \) and \( \frac{\partial R}{\partial x} = \frac{\partial}{\partial x}(0) = 0 \).
05
Compute \( \frac{\partial Q}{\partial x} \) and \( \frac{\partial P}{\partial y} \)
Calculate \( \frac{\partial Q}{\partial x} = \frac{\partial}{\partial x}(2x^2) = 4x \) and \( \frac{\partial P}{\partial y} = \frac{\partial}{\partial y}(y) = 1 \).
06
Apply the Curl Formula
Substitute the computed partial derivatives into the curl formula: \( abla \times \mathbf{v} = \left( 0 - 0, 0 - 0, 4x - 1 \right) \).
07
Write the Final Answer
The curl of the vector field is \( abla \times \mathbf{v} = \langle 0, 0, 4x - 1 \rangle \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Curl of a Vector Field
The curl of a vector field is a fascinating concept in vector calculus, representing how a vector field circulates around a point. To conceptualize this, imagine water swirling around a tiny paddle wheel. The curl measures the wheel's turning speed and direction at a point in the field.
- The mathematical expression for curl applies to vector fields in 3D space.
- For a vector field composed of components \( \mathbf{v} = \langle P, Q, R \rangle \), the curl is \( abla \times \mathbf{v} = \left( \frac{\partial R}{\partial y} - \frac{\partial Q}{\partial z}, \frac{\partial P}{\partial z} - \frac{\partial R}{\partial x}, \frac{\partial Q}{\partial x} - \frac{\partial P}{\partial y} \right) \).
- The result of the curl operation is another vector, indicating how the field rotates about a point.
Partial Derivatives
Partial derivatives play a key role in calculating the curl of a vector field. They provide a way of understanding how a function changes with respect to one variable while keeping the others constant.
- When finding the curl, partial derivatives, such as \( \frac{\partial R}{\partial y} \) or \( \frac{\partial Q}{\partial x} \), isolate the effect of changing one variable.
- The symbol \( \frac{\partial }{\partial x} \) represents the rate of change with respect to \( x \).
- In the given vector field \( \mathbf{v} = \langle y, 2x^2, 0 \rangle \), calculating these derivatives, such as \( \frac{\partial Q}{\partial x} = 4x \) and \( \frac{\partial P}{\partial y} = 1 \), helps assemble the curl vector.
Cartesian Coordinates
Cartesian coordinates form the backbone of expressing vector fields in a familiar 3D space. It is a simple and practical system for describing locations and transformations within a vector calculus framework.
- The coordinates \( (x, y, z) \) describe the position of points in 3-dimensional space.
- Vector fields are often represented as \( \mathbf{v} = \langle P, Q, R \rangle \), where each component aligns with a Cartesian axis.
- Using Cartesian coordinates allows us to easily apply operations like curl, gradient, and divergence on vector fields.