Problem 41
Question
A quantity \(P\) is inversely proportional to the cube of a quantity \(R\). Solve for \(R\) in terms of \(P\). Is \(R\) inversely proportional or proportional to a positive power of \(P ?\) What power?
Step-by-Step Solution
Verified Answer
Answer: R is inversely proportional to a positive power of P.
1Step 1: Write the relationship between P and R
Given that \(P\) is inversely proportional to the cube of \(R\), we can write the relationship as \(P = \frac{k}{R^3}\), where \(k\) is the constant of proportionality.
2Step 2: Solve for R in terms of P
We want to isolate \(R\) in the equation \(P = \frac{k}{R^3}\). First, we can multiply both sides of the equation by \(R^3\) to get rid of the denominator:
\(PR^3 = k\)
Now, we need to get \(R\) by itself, so we can take the cube root of both sides to get:
\(R = \sqrt[3]{\frac{k}{P}}\)
3Step 3: Analyze R's relationship to P
Looking at the equation we found in Step 2, \(R = \sqrt[3]{\frac{k}{P}}\), we can see that \(R\) is inversely proportional to the cube root of \(P\). This can also be written as \(R \propto P^{-1/3}\).
Therefore, \(R\) is inversely proportional, not proportional, to a positive power of \(P\), with a power of \(-1/3\).
Key Concepts
Cube RootConstant of ProportionalityPower Function
Cube Root
The cube root is a fundamental mathematical operation that involves finding a number which, when multiplied by itself three times, gives the original number. It's represented by the symbol \( \sqrt[3]{} \). This operation undoes the process of cubing a number.
When we deal with problems involving inverse proportionality and cube roots, it becomes essential to isolate variables using cube roots to solve for unknowns. In the context of this exercise, if we have a quantity \( R \) being isolated using the cube root, our goal is to find a value of \( R \) such that when raised to the third power (cubed), it fulfills the condition set in the equation.
For example, if you know that \( R^3 = \frac{k}{P} \), then taking the cube root of both sides gives you \( R = \sqrt[3]{\frac{k}{P}} \). The cube root allows us to unlock the value of \( R \), revealing its relationship with the other variables in the equation.
When we deal with problems involving inverse proportionality and cube roots, it becomes essential to isolate variables using cube roots to solve for unknowns. In the context of this exercise, if we have a quantity \( R \) being isolated using the cube root, our goal is to find a value of \( R \) such that when raised to the third power (cubed), it fulfills the condition set in the equation.
For example, if you know that \( R^3 = \frac{k}{P} \), then taking the cube root of both sides gives you \( R = \sqrt[3]{\frac{k}{P}} \). The cube root allows us to unlock the value of \( R \), revealing its relationship with the other variables in the equation.
- Useful in solving equations where a variable is cubed
- Helps in finding the original number from its cube
- Common in mathematics involving volumes and scaling
Constant of Proportionality
The constant of proportionality is a key component when expressing relationships between variables in proportionality equations. It provides the scale factor that modifies one variable based on another.
In inverse proportionality, we denote the relationship as \( P = \frac{k}{R^3} \), where \( k \) is the constant of proportionality. This constant \( k \) is crucial because it maintains the equation's balance, adjusting the ratio of change between \( P \) and the cube of \( R \).
Understanding this constant allows you to interpret how one quantity scales with another, ensuring the integrity of the relationship regardless of the specific values of \( P \) or \( R \). It is assumed constant unless otherwise noted.
In inverse proportionality, we denote the relationship as \( P = \frac{k}{R^3} \), where \( k \) is the constant of proportionality. This constant \( k \) is crucial because it maintains the equation's balance, adjusting the ratio of change between \( P \) and the cube of \( R \).
Understanding this constant allows you to interpret how one quantity scales with another, ensuring the integrity of the relationship regardless of the specific values of \( P \) or \( R \). It is assumed constant unless otherwise noted.
- Defines the specific relationship in proportionality equations
- Acts as a scaling factor
- A crucial component for maintaining equation balance
Power Function
A power function involves expressions where a variable is raised to a power. In your inverse proportionality example, power functions play a significant role in describing the relationship between \( P \) and \( R \).
Inverse proportionality with a power, like \( P = \frac{k}{R^3} \), indicates that \( P \) relates inversely to \( R \) raised to the third power. When isolating \( R \) in terms of \( P \), you uncover its relationship as a power function of \( P \): \( R = P^{-1/3} \). This shows how changes in \( P \) directly affect \( R \), where increasing \( P \) results in a decrease in \( R \), and vice versa.
Understanding the concept of power functions helps in analyzing these relationships and plotting them on a graph where one axis represents a variable and the other its power.
Inverse proportionality with a power, like \( P = \frac{k}{R^3} \), indicates that \( P \) relates inversely to \( R \) raised to the third power. When isolating \( R \) in terms of \( P \), you uncover its relationship as a power function of \( P \): \( R = P^{-1/3} \). This shows how changes in \( P \) directly affect \( R \), where increasing \( P \) results in a decrease in \( R \), and vice versa.
Understanding the concept of power functions helps in analyzing these relationships and plotting them on a graph where one axis represents a variable and the other its power.
- Describes relationships with variables raised to powers
- Useful in graphing and analyzing mathematical relationships
- Assists in solving complex mathematical models
Other exercises in this chapter
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