Newton's law of cooling states that the temperature of an object changes at a rate proportional to the difference between its temperature and that of its surroundings. If we measure temperature in degrees Celsius and time in minutes, the constant of proportionality k equals 0.3. Suppose the ambient temperature TA(t) is equal to a constant 47 degrees Celsius. Write the differential equation that describes the time evolution of the temperature of the object.
(a)
0.3(T - 47)
Suppose the ambient temperature TA(t) is 47cos(pi*t/30) degrees Celsius (time measured in minutes). Write the DE that describes the time evolution of the temperature of the object:
(b)
0.3(T - 47cos(pi*t/30))
If we measure time in hours, the differential equation in part (b) changes. What is the new differential equation? Use the letter s to denote time in hours.
(c)
-1/200(T - 47cos(pi*t/30))
If we measure time in hours and we also measure temperature in degrees Fahrenheit, the differential equation in part (c) changes even more. What is the new differential equation? Use the letter F to denote temperature in degrees Fahrenheit:
(d)
dF/ds = -9/1000(T - 47cos(pi*t/30)) + 32