Temperature in spherical jacket · Physics Brawl 2014 #FoL.2
Physics · thermodynamics
Problem
Consider Mr Spherical (whose shape, incidentally, happens to be perfectly spherical) that likes to wear a tight-fitting jacket of negligible thickness (compared to his radius). Wearing his jacket, Mr Spherical went outside for a walk. Once the thermal equilibrium between Mr Spherical and his surroundings was established, the temperatures at the inner and outer surfaces of his jacket could be measured to be 25°C and -5°C, respectively. Find the temperature (in degrees Celsius), which is measured exactly in the middle of the layer of Mr Spherical's jacket (i.e. half-way through the bulk of the layer).