Chapter 2: Problem 17
13–22 ? Express the statement as an equation. Use the given information to find the constant of proportionality. \(W\) is inversely proportional to the square of \(r .\) If \(r=6,\) then \(W=10 .\)
Short Answer
Expert verified
The constant of proportionality is 360.
Step by step solution
01
Understand Inverse Proportionality
When a quantity is inversely proportional to another, it means that as one quantity increases, the other decreases in such a way that their product remains constant. Here, we are told that \( W \) is inversely proportional to the square of \( r \). This implies that \( W \times r^2 = k \), where \( k \) is the constant of proportionality.
02
Set Up the Equation
Express the inverse proportionality as an equation. Since \( W \) is inversely proportional to \( r^2 \), we can write the equation as:\[ W = \frac{k}{r^2} \] where \( k \) is the constant of proportionality we need to find.
03
Substitute Known Values
We are given that \( r = 6 \) and \( W = 10 \). Substitute these values into the equation to find \( k \):\[ 10 = \frac{k}{6^2} \]
04
Solve for the Constant of Proportionality
Since \( 6^2 = 36 \), our equation becomes:\[ 10 = \frac{k}{36} \]Multiply both sides by 36 to solve for \( k \):\[ k = 10 \times 36 = 360 \]
05
Verify the Equation
Now that we have \( k = 360 \), substitute back into the inverse proportionality equation to verify:\[ W = \frac{360}{r^2} \] For \( r = 6 \), \( W = \frac{360}{36} = 10 \), which is consistent with the given values.
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Understanding the Constant of Proportionality
The constant of proportionality is a fixed value that relates two variables in a proportional relationship. In our problem, this constant is denoted by \( k \). When quantities are related by inverse proportionality, the constant ensures that as one variable increases, the other decreases in such a way that their product stays the same.
Here's a simple breakdown:
Here's a simple breakdown:
- In a typical inverse proportionality scenario, the equation takes the form \( x \times y = k \).
- In our specific example, we are given \( W \times r^2 = k \).
- This equation tells us how \( W \) and \( r^2 \) relate to each other through this constant \( k \), that keeps their product unchanged.
Grasping Inverse Variation
Inverse variation describes a relationship between two variables where one variable increases as the other decreases, in such a way that their product remains constant. This connection is the essence of inverse proportionality.
With inverse variation:
With inverse variation:
- The equation we use is \( y = \frac{k}{x} \), where \( k \) is the constant of proportionality.
- In our problem, the relationship of \( W \) with \( r^2 \) is described as \( W = \frac{k}{r^2} \).
- As \( r \) increases, \( r^2 \) increases as well, causing \( W \) to decrease for the equation to balance out.
Steps to Equation Solving
Solving equations with inverse proportionality involves understanding the setup and carefully replacing values to find unknowns. In our problem:
Here's the process step-by-step:
Here's the process step-by-step:
- Write the inverse proportionality equation based on the given relationship, in this case, \( W = \frac{k}{r^2} \).
- Substitute values that you know. Here, \( r = 6 \) and \( W = 10 \).
- Calculate to find \( k \): Substitute into the equation and solve for \( k \), giving us \( 10 = \frac{k}{36} \).
- Multiply both sides by the denominator to find \( k \): Here, \( k = 360 \).
- VERIFY: Substitute \( k \) back into your equation to check the correctness. Ensure your solution satisfies the original condition.