Math Problem Statement

A roasted turkey is taken from an oven when its temperature has reached 185 Fahrenheit and is placed on a table in a room where the temperature is 75 Fahrenheit. Give answers accurate to at least 2 decimal places.

(a) If the temperature of the turkey is 142 Fahrenheit after half an hour, what is its temperature after 45 minutes?

Solution

To solve this problem, we'll use Newton's Law of Cooling, which states that the rate of change of the temperature of an object is proportional to the difference between its temperature and the ambient temperature. Mathematically, it's expressed as:

dTdt=k(T(t)Tambient)\frac{dT}{dt} = -k(T(t) - T_{\text{ambient}})

where:

  • T(t)T(t) is the temperature of the object at time tt.
  • TambientT_{\text{ambient}} is the ambient temperature.
  • kk is a constant.

The solution to this differential equation is:

T(t)=Tambient+(T0Tambient)ektT(t) = T_{\text{ambient}} + (T_0 - T_{\text{ambient}})e^{-kt}

where:

  • T0T_0 is the initial temperature of the object at t=0t = 0.
  • tt is the time elapsed.

Given:

  • Initial temperature T0=185FT_0 = 185^\circ \text{F}
  • Ambient temperature Tambient=75FT_{\text{ambient}} = 75^\circ \text{F}
  • Temperature after 30 minutes T(30)=142FT(30) = 142^\circ \text{F}

First, we need to find the constant kk using the given information. Then, we can use that value to find the temperature after 45 minutes.

Step 1: Find kk

Using the formula for T(t)T(t):

142=75+(18575)e30k142 = 75 + (185 - 75)e^{-30k}

Simplify and solve for kk:

14275=110e30k142 - 75 = 110e^{-30k}

67=110e30k67 = 110e^{-30k}

67110=e30k\frac{67}{110} = e^{-30k}

ln(67110)=30k\ln\left(\frac{67}{110}\right) = -30k

k=130ln(67110)k = -\frac{1}{30} \ln\left(\frac{67}{110}\right)

Step 2: Find the temperature after 45 minutes

Now, using the value of kk we calculated, we substitute it into the formula to find T(45)T(45):

T(45)=75+110e45kT(45) = 75 + 110e^{-45k}

Let's calculate this step by step.

Calculation

I'll compute the value of kk and then find T(45)T(45).import math

Given values

T_ambient = 75 # Ambient temperature T0 = 185 # Initial temperature of the turkey T_30 = 142 # Temperature after 30 minutes t1 = 30 # Time in minutes (half an hour) t2 = 45 # Time in minutes (45 minutes)

Calculate the constant k

k = -(1 / t1) * math.log((T_30 - T_ambient) / (T0 - T_ambient))

Calculate the temperature after 45 minutes

T_45 = T_ambient + (T0 - T_ambient) * math.exp(-k * t2) T_45The temperature of the turkey after 45 minutes is approximately 127.29°F.

Would you like more details or have any other questions?

Here are some related questions you might find interesting:

  1. How would the temperature change after 1 hour?
  2. What if the ambient temperature was different?
  3. How does the rate constant kk affect the cooling process?
  4. What happens if the turkey was removed from the oven at a different initial temperature?
  5. How could this model be adjusted for different cooling conditions?

Tip: Newton's Law of Cooling can be applied to various scenarios, such as cooling beverages or even forensic investigations to estimate the time of death.

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Math Problem Analysis

Mathematical Concepts

Differential Equations
Newton's Law of Cooling

Formulas

Newton's Law of Cooling: T(t) = T_ambient + (T0 - T_ambient)e^(-kt)

Theorems

Newton's Law of Cooling

Suitable Grade Level

High School