Newton’s Law of Cooling – ugrad.math.ubc.ca

Given: The rate of change of the temperature , is (by Newton’s Law of Cooling) proportional to the difference between the temperature of the soup and the ambient temperature This means that: Here a bit of care is needed: Clearly if the soup is hotter than the water in the sink , then the soup is cooling down which means that the derivative should be negative.

http://www.ugrad.math.ubc.ca/coursedoc/math100/notes/diffeqs/cool.html