Newton's Cooling Law

Calculus Level 3

Newton’s Law of Cooling states that the rate of cooling of an object is proportional to the temperature difference between the object and its surroundings, If we let T i Ti be the temperature of the object at time t t and T s Ts be the temperature of the surroundings, then we can formulate Newton’s Law of Cooling as a differential equation: d T / d t = k ( T i T s ) dT/dt =k(Ti- Ts)

If a bottle of soda pop at room temperature ( 72 ° F ) (72°F) is placed in a refrigerator where the temperature is 44 ° F 44°F and after half an hour the soda pop has cooled to 61 ° F 61°F , then what is the temperature of the soda pop after another half hour?

*Give answer in Fahrenheit *

Use Floor function to round answer


The answer is 54.

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1 solution

Amal Hari
Dec 17, 2018

Initial Temperature difference

is Temp. of refrigerator - Temp. of pop= 28.

Then, initially at t=0

Let

Ts=temp. of refrigerator,

Ti =initial temp. of pop,

To be the temp. difference.

T i T s = T o = 28 e ( k 0 ) = 28 . Ti-Ts=To=28*e^{(k*0)=28}.

Tf-Ts=To e^(k t)

Tf=61

Tf-Ts=61-44=17

Tf=To e^(k 30) , I took time in minutes.

solving for k we get k = 0.01663 k=-0.01663 approx

Then let T1 be the temperature after 1 hour,

It follows T 1 T s = T o e ( 0.01663 60 ) T1-Ts=To * e^{(-0.01663*60)}

T 1 = T s + T o e ( . 9978 ) T1=Ts+To*e^{(-.9978)}

T1=44+ 28*0.3686

T1=44+10.3233

T1=54 approx.

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