Chapter 6: Problem 31
Find the solution \(y(t)\) by recognizing each differential equation as determining unlimited, limited, or logistic growth, and then finding the constants. \(y^{\prime}=3 y(10-y)\) \(v(0)=20\)
Short Answer
Expert verified
The solution is \( y(t) = \frac{10}{1 - 0.5e^{-3t}} \).
Step by step solution
01
Identify the Type of Growth
The given differential equation is \[ y^{\prime} = 3y(10-y) \].This equation is in the form of a logistic growth model, as it resembles the general structure \[ y^{\prime} = ky(M-y) \],where \( M \) is the carrying capacity and \( k \) is the growth rate. Here, \( k = 3 \) and \( M = 10 \).
02
Set Up the Logistic Equation
The logistic growth equation can be defined as\[ y(t) = \frac{M}{1 + \left( \frac{M - y_0}{y_0} \right)e^{-kt}} \],where \( y_0 = v(0) \) is the initial value. According to the problem, \( y_0 = 20 \), and the carrying capacity \( M = 10 \).
03
Substitute Given Values
Substitute \( M = 10 \), \( y_0 = 20 \), and \( k = 3 \) into the logistic growth formula:\[ y(t) = \frac{10}{1 + \left( \frac{10 - 20}{20} \right)e^{-3t}} \].
04
Simplify the Equation
Calculate the fraction inside the exponential term:\( \frac{10 - 20}{20} = -0.5 \). Substitute back to the equation:\[ y(t) = \frac{10}{1 - 0.5e^{-3t}} \].
05
Write the Solution
The final solution for the differential equation is\[ y(t) = \frac{10}{1 - 0.5e^{-3t}} \].
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Logistic Growth
Logistic growth is a common model in biology that describes how populations grow in an environment with limited resources. Unlike exponential growth, which assumes unlimited resources, logistic growth includes the impact of a carrying capacity, which is the maximum population size that the environment can sustain. This model is represented by a specific type of differential equation.
- The general form of a logistic growth differential equation is: \( y' = ky(M-y) \)
- In this equation, \( M \) represents the carrying capacity, \( k \) is the growth rate, and \( y \) is the population size.
- The solution to the logistic growth equation is a function that shows how the population size changes over time.
Carrying Capacity
Carrying capacity is a key component in understanding logistic growth. It is crucial to comprehending the limits a population faces due to environmental constraints like food, space, and other resources.
- Carrying capacity, often denoted as \( M \), is the maximum number of individuals that an environment can support without degradation.
- In logistic growth equations, \( M \) affects how quickly the population approaches stability.
- As the population size, \( y \), gets closer to \( M \), the growth rate decreases, indicating resource limitations.
Initial Value Problem
An initial value problem in the context of differential equations involves finding a specific solution that passes through a given initial condition. This requires both an equation and an initial value from which the solution will begin.
- An initial value problem specifies the value of the solution at a starting point, typically expressed as \( y(0) = y_0 \).
- In logistic growth, the initial value \( y_0 \) is essential for determining the particular solution that describes the population's growth from a known starting size.
- The solution not only solves the differential equation but also satisfies this initial condition.