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Write an equation or differential equation for the given information. Advertising spreads the news of a commodity through a community of size \(L\) at a rate that is jointly proportional to the number of people \(p\) who have heard about the commodity and the number of people who have not heard about the commodity.

Short Answer

Expert verified
\( \frac{dp}{dt} = k \cdot p \cdot (L - p) \) is the differential equation.

Step by step solution

01

Interpreting the Problem

The question relates to finding a model for the spread of information throughout a community. We know that the rate at which the news spreads depends on both the people who have heard the news and those who haven't.
02

Define Variables

Let \( p \) be the number of people who have heard about the commodity at time \( t \). Hence, the number of people who have not heard about it is \( L - p \), where \( L \) is the total size of the community.
03

Express the Rate of Change

The problem states the rate is jointly proportional to those who have and have not heard the commodity. This means that the rate of change \( \frac{dp}{dt} \) is proportional to the product \( p(L-p) \).
04

Write the Differential Equation

The expression for the rate of change is \( \frac{dp}{dt} = k \cdot p \cdot (L - p) \), where \( k \) is the constant of proportionality. This equation reflects the dynamic nature of information spread across the population.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Information Spread Model
The information spread model described here aims to illustrate how news or a product advertisement propagates through a community. This spread occurs when people share information, like a domino effect. The rate at which news spreads can vary and is influenced by several factors, including how many people are already aware versus those who remain uninformed. In mathematical terms, we express this dynamic with a differential equation, which equates the rate of change of informed individuals to the product of two groups: the informed and the uninformed. This relationship is crucial, as it mirrors real-world scenarios where news can spread more rapidly when a majority of people are either learning or sharing it. This model offers insight into how effective information dissemination strategies could be optimized. Understanding this can help tailor marketing campaigns or public health messages to ensure maximum reach and efficiency.
Joint Proportionality
Joint proportionality is central to our discussion on differential equations in the spread of information. It means that the rate of change depends on the multiplication of factors, rather than just their sum or linear combination. Here, the key factors are the number of people informed, denoted by \( p \), and those uninformed, represented as \( L-p \), where \( L \) is the total population size.This creates the expression \( k \cdot p \cdot (L - p) \), showing that the spread rate increases with each informed and uninformed person interacting. Joint proportionality allows the model to consider both groups simultaneously, ensuring the rate of information dissemination accurately reflects real interaction dynamics.The constant \( k \) indicates how forceful or fast this spread can happen, influenced by factors such as message appeal or frequency of interactions between individuals. Thus, this model provides a holistic view of how different factors can conspire to determine the speed of information spread.
Population Dynamics
In the context of this exercise, population dynamics help us comprehend how different segments of a community interact and change over time. Through the lens of our differential equation, we view the community not just as static groups but as dynamic participants in spreading a message or news.Population dynamics in this model reflect the interplay between the informed and uninformed groups. This interaction is captured in the formula \( \frac{dp}{dt} = k \cdot p \cdot (L - p) \), showing the growth of informed people over time. The equation considers how individual contributions by each group affect the overall information propagation.The model provides insights into scenarios such as rumors spreading or advertisement reach potential. By understanding population dynamics, we can better predict how information will likely travel through and influence a community. This is invaluable for planning everything from marketing strategies to public information campaigns.

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Most popular questions from this chapter

Medicine The rate of change with respect to time of the quantity \(q\) of pain reliever in a person's body \(t\) hours after the individual takes the medication is proportional to the quantity of medication remaining. Assume that 2 hours after a person takes 200 milligrams of a pain reliever, onehalf of the original dose remains. a. Write a differential equation for the rate of change of the quantity of pain reliever in the body. b. Find a particular solution for this differential equation. c. How much pain reliever will remain after 4 hours; after 8 hours?

Motion Laws When a spring is stretched and then released, it oscillates according to two laws of physics: Hooke's law and Newton's second law. These two laws combine to form the following differential equation in the case of free, undamped oscillation: $$ m \frac{d^{2} x}{d t^{2}}+k x=0 $$ where \(m\) is the mass of an object attached to the spring, \(x\) is the distance the spring is stretched beyond its standard length with the object attached (its equilibrium point), \(t\) is time, and \(k\) is a constant associated with the strength of the spring. Consider a spring with \(k=15\) from which is hung a 30 -pound weight. The spring with the weight attached stretches to its equilibrium point. The spring is then pulled 2 feet farther than its equilibrium and released. a. Write a differential equation describing the acceleration of the spring with respect to time \(t\) measured in seconds. Use the fact that mass \(=\frac{\text { weight }}{\mathrm{g}},\) where \(g\) is the gravi- tational constant, 32 feet per second per second. b. Write a particular solution for this differential equation. Use the fact that when the spring is first released, its velocity is \(0 .\) c. Graph this solution over several periods and explain how to interpret the graph. d. How quickly is the mass moving when it passes its equilibrium point?

Write an equation or differential equation for the given information. The rate of change with respect to time \(t\) of the amount \(A\) that an investment is worth is proportional to the amount in the investment.

Write a differential equation expressing the information given and, when possible, find a general solution for the differential equation. The rate of change with respect to time \(t\) of the demand \(D\) for a product is decreasing in proportion to the demand at time \(t\).

Sculptures The average quantity of sculptures consumers will demand can be modeled as $$ D(p)=-1.003 p^{2}-20.689 p+850.375 \text { sculptures } $$ and the average quantity producers will supply can be modeled as $$ S(p)=\left\\{\begin{array}{ll} 0 & \text { for } p<4.5 \\ 0.26 p^{2}+8.1 p+250 & \text { for } p \geq 4.5 \end{array}\right. $$ where \(S(p)\) is measured in sculptures and the market price is \(p\) hundred dollars per sculpture. a. How much are consumers willing and able to spend for 20 sculptures? b. How many sculptures will producers supply at \(\$ 500\) per sculpture? Will supply exceed demand at this quantity? c. Calculate the total social gain when sculptures are sold at the equilibrium price.

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