Two solid spheres of identical mass, radius, surface finish, and emissivity are heated uniformly to 150 °C and then suspended in still air at 25 °C. Sphere X is made of stainless steel, and sphere Y is made of aluminum. Their specific heats are given below.
Material Specific heat (J kg⁻¹ °C⁻¹)
Stainless steel 500
Aluminum 900
(a) Which sphere reaches 50 °C first? State your answer and justify it qualitatively.
(b) Estimate the ratio of the initial thermal energy stored in sphere Y to that in sphere X. Show your reasoning using the numerical data provided.
(c) Discuss why making the spheres identical in size and surface properties was necessary for isolating the effect examined in parts (a) and (b).