Chapter 20: Problem 8
In Exercises \(6-13,\) compute the curl of the vector field. $$\vec{F}=(-x+y) \vec{i}+(y+z) \vec{\jmath}+(-z+x) \vec{k}$$
Short Answer
Expert verified
The curl of \( \vec{F} \) is \( -\hat{i} - \hat{\jmath} - \hat{k} \)."
Step by step solution
01
Identify the Vector Field Components
The vector field \( \vec{F} \) can be written in component form as \( \vec{F} = (-x + y) \hat{i} + (y + z) \hat{\jmath} + (-z + x) \hat{k} \). Here, the components of \( \vec{F} \) are \( P = -x + y \), \( Q = y + z \), and \( R = -z + x \).
02
Recall the Formula for Curl
The curl of a vector field \( \vec{F} = P \hat{i} + Q \hat{\jmath} + R \hat{k} \) is given by \( abla \times \vec{F} = \left( \frac{\partial R}{\partial y} - \frac{\partial Q}{\partial z} \right) \hat{i} + \left( \frac{\partial P}{\partial z} - \frac{\partial R}{\partial x} \right) \hat{\jmath} + \left( \frac{\partial Q}{\partial x} - \frac{\partial P}{\partial y} \right) \hat{k} \).
03
Compute Partial Derivatives for Each Component
- \( \frac{\partial R}{\partial y} = \frac{\partial}{\partial y} (-z + x) = 0 \) because \( x \) and \( z \) are constants with respect to \( y \).- \( \frac{\partial Q}{\partial z} = \frac{\partial}{\partial z} (y + z) = 1 \).- \( \frac{\partial P}{\partial z} = \frac{\partial}{\partial z} (-x + y) = 0 \) because \( x \) and \( y \) are constants with respect to \( z \).- \( \frac{\partial R}{\partial x} = \frac{\partial}{\partial x} (-z + x) = 1 \).- \( \frac{\partial Q}{\partial x} = \frac{\partial}{\partial x} (y + z) = 0 \) because \( y \) and \( z \) are constants with respect to \( x \).- \( \frac{\partial P}{\partial y} = \frac{\partial}{\partial y} (-x + y) = 1 \).
04
Substitute Partial Derivatives into Curl Formula
Substitute the partial derivatives into the curl formula:\[abla \times \vec{F} = \left( 0 - 1 \right) \hat{i} + \left( 0 - 1 \right) \hat{\jmath} + \left( 0 - 1 \right) \hat{k} = -\hat{i} - \hat{\jmath} - \hat{k}.\]
05
Write the Final Result
The curl of the vector field \( \vec{F} \) is \( abla \times \vec{F} = -\hat{i} - \hat{\jmath} - \hat{k} \).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Curl
The curl of a vector field is a fundamental concept in vector calculus. It essentially measures the tendency of the field to cause rotation around a point. Imagine placing a small paddlewheel at any point in the field and observing its rotation. If the wheel rotates, the field has a non-zero curl at that point. This rotation is most commonly examined in fluid dynamics and electromagnetism.
To compute the curl, we utilize the formula for the curl of a vector field \( \vec{F} = P \hat{i} + Q \hat{\jmath} + R \hat{k} \). It is given as:
To compute the curl, we utilize the formula for the curl of a vector field \( \vec{F} = P \hat{i} + Q \hat{\jmath} + R \hat{k} \). It is given as:
- \( abla \times \vec{F} = \left( \frac{\partial R}{\partial y} - \frac{\partial Q}{\partial z} \right) \hat{i} + \left( \frac{\partial P}{\partial z} - \frac{\partial R}{\partial x} \right) \hat{\jmath} + \left( \frac{\partial Q}{\partial x} - \frac{\partial P}{\partial y} \right) \hat{k} \)
Vector Field
A vector field is a mathematical function that assigns a vector to every point in space. Picture it as a field filled with arrows, each pointing in a specific direction and having a certain magnitude. These vectors can represent various physical quantities such as force, velocity, or acceleration, depending on the context.
In our exercise, we were given the vector field \( \vec{F} = (-x+y) \hat{i} + (y+z) \hat{\jmath} + (-z+x) \hat{k} \). Each component of the vector field corresponds to a coordinate direction:
In our exercise, we were given the vector field \( \vec{F} = (-x+y) \hat{i} + (y+z) \hat{\jmath} + (-z+x) \hat{k} \). Each component of the vector field corresponds to a coordinate direction:
- \(-x + y\) is aligned with the \( \hat{i} \) direction
- \(y + z\) lies along the \( \hat{\jmath} \) direction
- \(-z + x\) is in the \( \hat{k} \) direction
Partial Derivatives
Partial derivatives are a vital tool in calculus, especially when dealing with functions of more than one variable. A partial derivative measures how a function changes as one of its variables is varied, while keeping the other variables constant.
When computing the curl in our solution, several partial derivatives were calculated:
When computing the curl in our solution, several partial derivatives were calculated:
- \( \frac{\partial R}{\partial y} = 0 \)
- \( \frac{\partial Q}{\partial z} = 1 \)
- \( \frac{\partial P}{\partial z} = 0 \)
- \( \frac{\partial R}{\partial x} = 1 \)
- \( \frac{\partial Q}{\partial x} = 0 \)
- \( \frac{\partial P}{\partial y} = 1 \)
Multivariable Calculus
Multivariable calculus extends single-variable calculus to functions of several variables. It is essential for understanding phenomena where multiple factors are at play. In our example, we dealt with a vector field, a primary topic in multivariable calculus.
- It uses partial derivatives to describe how functions change with respect to each variable.
- It encompasses operations like curl and divergence, which help analyze vector fields.