question_answer 34)

                  A glass full of hot milk is poured on the table. It beings to cool gradually. Which of the following is correct?                 (a) The rate of cooling is constant till milk attains the temperature of the surrounding.                 (b) The temperature of milk falls off exponentially with time.                 (c) While cooling, there is a flow of heat from milk to the surrounding as well as from surrounding to the milk but the net flow of heat is from milk to the surrounding and that is why it cools.                 (d) All three phenomenon, conduction, convection and radiation are responsible for the loss of heat from milk to the surroundings.                

Answer:

                  (a, c, d) According no Newton?s law of cooling, the rate of cooling of a body is directly proportional to the temperature difference between the body and its surroundings. Every body above OK emits heat radiations.