A small sphere ( 12.7 mm diameter) is made of copper. The initial temperature of the sphere is 66 C. At t = 0 the sphere is inserted into an air stream at 27 C. After 69 seconds of exposure to the air stream the temperature of the surface of the sphere is measured to be 55 C. Assuming the sphere acts as a lumped mass (i.e. negligible temperature gradients within the sphere) determine the heat transfer coefficient on the surface of the sphere, i.e. h. Is the assumption of a lumped mass justified?