The surface of a sphere of unknown density is cooled from 900C to 550C by submersion in a bath at 300C. Convection occurs with a coefficient of 60 W/(m2 K) The spheres diameter is 42 mm. The heat capacity of the sphere is 1700 J/(kg K) and its thermal conductivity is 1.50 W/(m K). If it takes 120 seconds for the cooling process to occur, what is the density of the material? You may neglect radiation.

Using: Biot number and Fourier number.