Re: What does the constant,k, in Newtons Law of Cooling represent?

Hi Ken,

actually both of those statements are right: k is a constant - but the value of this constant depends on the object, in other words: every cooling object has (in most cases) a different value of k.

And there are a few obvious reasons - take for example the surface of the object. If you have a certain mass and a certain given temperature (let's assume standard pressure) then your body has a certain enthalpy, means, a certain value of "saved energy", depending on C_p, the heap capacity. Now imagine this object with mass m in the form of a sphere, the form with smallest surface at given volume (and mass in this case). Then imagine it in the form of a cuboid with two very long sides and one very short sides - very flat, nearly a rectangle. It's obvious that the rate of cooling depends on the surface (nearly proportional, probably) and that the flat cuboid cools down much faster than the sphere.

And actually - I can imagine no other variables in this case, of course if you keep mass and material constant.

If you are interested, click on
http://www.math. pitt.edu/~frank/0250/newton/newton/ (a house has k=3 ) or
http://www.sosmath.com/diffeq/first/application/newton/newton.html it's a general explanation of Newton's law.

I hope that's okay,

bye,

Andreas