/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 76 Coal consumption A country prese... [FREE SOLUTION] | 91Ó°ÊÓ

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Coal consumption A country presently has coal reserves of 50 million tons. Last year 6.5 million tons of coal was consumed. Past years' data and population projections suggest that the rate of consumption \(R\) (in million tons/year) will increase according to the formula \(R=6.5 e^{0.02 t}\) and the total amount \(T\) (in million tons) of coal that will be used in t years is given by the formula \(T=325\left(e^{0.02 t}-1\right) .\) If the country uses only its own resources, when will the coal reserves be depleted?

Short Answer

Expert verified
The coal reserves will be depleted in approximately 7.16 years.

Step by step solution

01

Understand the Problem

We need to determine when the coal reserves in the country, which are initially 50 million tons, will be depleted. The consumption rate and total amount of coal used over time are given by the formulas: \( R = 6.5 e^{0.02t} \) and \( T = 325(e^{0.02t} - 1) \), respectively.
02

Set Up the Equation

To find when the reserves are depleted, set the total amount used \( T \) equal to the initial reserves of 50 million tons: \[ 325(e^{0.02t} - 1) = 50 \] and solve for \( t \).
03

Isolate the Exponential Term

Divide both sides by 325 to isolate the exponential expression:\[ e^{0.02t} - 1 = \frac{50}{325} \] \[ e^{0.02t} = 1 + \frac{50}{325} \]
04

Simplify the Equation

Calculate \( \frac{50}{325} \) to simplify the right-hand side:\[ e^{0.02t} = 1 + 0.153846 \]\[ e^{0.02t} = 1.153846 \]
05

Solve for t using Logarithms

Take the natural logarithm (ln) of both sides to solve for \( t \):\[ \ln(e^{0.02t}) = \ln(1.153846) \] \[ 0.02t = \ln(1.153846) \] \[ t = \frac{\ln(1.153846)}{0.02} \]
06

Calculate the Value of t

Use a calculator to find \( t \):\[ t = \frac{0.1431}{0.02} = 7.155 \] So, the coal reserves will be depleted in approximately 7.16 years.

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Key Concepts

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

Coal Consumption
Coal consumption is a crucial topic in understanding how natural resources are used and depleted. In our example, a country starts with 50 million tons of coal. Each year, more coal is consumed, and this rate of consumption isn't constant; it changes over time. Last year, the country consumed 6.5 million tons of coal. This level of consumption is expected to increase, based on population growth and industrial activities. Such increases are typically modeled using exponential growth equations, because the rate is not just adding additional tons each year, but increasing by a multiplying factor. Understanding how these factors influence coal consumption helps plan for resource sustainability and energy policies. Tracking these changes over time is essential for preparing for potential shortages or transitions to other energy sources.
Depletion Time
Depletion time refers to when the coal reserves will run out, given the current and future consumption trends. Calculating depletion time is a critical task for resource management and planning. In our exercise, we determined the depletion by setting the total amount of coal used over time equal to the initial amount of coal available. This is done mathematically to predict when the reserves will hit zero. By solving an exponential equation, we found that the coal reserves would last approximately 7.16 years. Understanding depletion time helps governments and organizations make informed decisions about resource management, conservation, and innovation in alternative energy sources.
Logarithmic Calculation
Logarithmic calculations are vital in solving exponential equations, especially when it comes to determining time frames. In our case, to find out how long the coal will last, we needed to solve an equation involving an exponential function.Exponential equations like those seen in growth models often require the use of logarithms for simplification. By taking the natural logarithm of both sides of the equation \[ e^{0.02t} = 1.153846 \]we could isolate the variable t. This transformation is crucial because it allows us to retrieve the exponent, hence ‘solving’ the problem technically. Understanding how to apply logarithms in such situations is essential for dealing with exponential growth scenarios, like resource depletion.
Exponential Functions
Exponential functions are mathematical expressions that describe growth or decay processes, such as population increases or resource consumption over time.In this exercise, the exponential function models how coal consumption rises: \[ R = 6.5 e^{0.02t} \]This reflects not a simple increase, but a form of growth where each step is compounded by a percentage. The essence of exponential growth is that it accelerates over time, much like compounding interest in a savings account.Having a handle on exponential functions is important because they offer a way to predict and understand real-world processes. They allow policymakers and scientists to forecast future resource needs and challenges efficiently.

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