A sphere, a cube and a thin circular pate are heated to the same temperature. If they are made of same material and have equal masses, determine which of these three object cools the fastest and which one cools the slowest?

Explanation

According to Stefan's law, the rate of cooling of a body is given by
`(-dT)/(dt)=(esigmaA)/(mc)(T^4-T_0^4)`
Here e,`sigma`,c,T and `T_0` are constants for all the three objects, therefore
`(-dT)/(dt)propA`
Since the surface area of the plate is maximum and that of the sphere is minimum for the given mass, therefore, the circular plate cools the fastest, and the sphere cools the slowest.