Beachbum posted a question
A winter hiker's body generates heat at a rate up to a maximum value of 126 W. She is hiking on a brisk day in which the outdoor temperature is 9°C, while wearing a jacket with goose down insulation. How thick must the jacket be so that she can maintain a normal body temperature? Assume her surface area for heat flow (the jacket) is 1.5 m2 and that all of her body heat flows out through the jacket. (Assume the thermal conductivity to be 0.025 W/m · K.)