Two spherical balls A and B made of the same material, are heated to the same temperature. They are then placed in identical surroundings. If the diameter of A is twice that of B, the ratio of rates of cooling of A and B will be
4:1
The rate of cooling is directly proportional to the surface area if the balls are made up of the same material. Since the surface area of A is 4 times that of B, the ratio of rate of cooling will be 4:1 and the correct choice is (c).