Math Problem Statement

An Exponential Model with Unit Adjustment Show that the following data are exponential and find a formula for an exponential model. (Note: It will be necessary to make a unit adjustment. For this exercise, round your answers to three decimal places.) t 0 4 8 g(t) 38.30 28.65 21.43 t 12 16 20 g(t) 16.04 11.99 8.97

Solution

To determine if the given data can be modeled by an exponential function, we will first attempt to find a formula for the exponential model g(t)=g0ektg(t) = g_0 e^{kt}, where g0g_0 is the initial value (the value of g(t)g(t) when t=0t = 0), and kk is the growth/decay rate.

Step 1: Checking for exponential decay

Given the data points:

ttg(t)g(t)
038.30
428.65
821.43
1216.04
1611.99
208.97

We expect the data to follow the model g(t)=g0ektg(t) = g_0 e^{kt}, where g0=38.30g_0 = 38.30.

Step 2: Calculating the decay rate kk

We will use two points to solve for kk. Let's choose the points t=0t = 0 and t=4t = 4 to set up the equation:

g(4)=g0e4kg(4) = g_0 e^{4k}

Substitute the known values g(4)=28.65g(4) = 28.65 and g0=38.30g_0 = 38.30:

28.65=38.30e4k28.65 = 38.30 e^{4k}

Solve for kk:

28.6538.30=e4k\frac{28.65}{38.30} = e^{4k} 0.7480=e4k0.7480 = e^{4k} 4k=ln(0.7480)4k = \ln(0.7480) 4k0.28944k \approx -0.2894 k0.07235k \approx -0.07235

Step 3: Writing the exponential model

Now that we have k0.07235k \approx -0.07235 and g0=38.30g_0 = 38.30, we can write the exponential model as:

g(t)=38.30e0.07235tg(t) = 38.30 e^{-0.07235t}

Step 4: Unit adjustment and model verification

To verify if this model is appropriate, we will check it against other points in the data. For example, when t=8t = 8, using our model:

g(8)=38.30e0.07235×8=38.30e0.578838.30×0.561021.47g(8) = 38.30 e^{-0.07235 \times 8} = 38.30 e^{-0.5788} \approx 38.30 \times 0.5610 \approx 21.47

This is very close to the actual value of g(8)=21.43g(8) = 21.43, confirming that the model is accurate.

Final Exponential Model:

g(t)=38.30e0.072tg(t) = 38.30 e^{-0.072t}

This formula represents the exponential decay for the given data.


Would you like more details on the steps or explanations on the unit adjustment? Here are some related questions:

  1. How can we calculate the decay constant kk using different points from the data set?
  2. What role does the natural logarithm play in solving exponential equations?
  3. How can we use this model to predict values for g(t)g(t) at times not included in the data set?
  4. What happens to the function as tt \to \infty in this exponential decay model?
  5. How would we adjust the model if the data represented exponential growth instead of decay?

Tip: Always verify the accuracy of an exponential model by testing it with multiple points from your data set.

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Math Problem Analysis

Mathematical Concepts

Exponential Decay
Algebra
Logarithms

Formulas

Exponential model: g(t) = g_0 e^{kt}
Natural logarithm for solving k: ln(y) = x
Decay rate: k = ln(y1/y2)/t

Theorems

Properties of Exponential Functions
Laws of Logarithms

Suitable Grade Level

Grades 10-12