You have been given with a cup of coffee which is too hot to drink .Which among the following is the best method to cool it? Why?
(i) Placing it in a beaker containing water
(2) Placing it on the surface of wood
(3) Placing it on the surface of an iron block

Explanation

The best method to cool it is to place it in water .The heat tranfer rate with wood is less compared to the iron block but when it placed on an iron block only the bottom surface is in conatact with the iron block but whne it is placed in a beaker containing water the heat transfer rate is also more hence the cooling effect is more when it is placed in water