A cup of coffee has an initial temperature of and is left to cool in a room that is…
PHYSICS · Multi-part · CBSE · Physics · Thermal Properties of Matter · Thermal Properties of Matter
Problem
A cup of coffee has an initial temperature of 90∘C and is left to cool in a room that is maintained at a constant temperature of 25∘C. The temperature of the coffee is found to be 70∘C after 10 minutes and 55∘C after 25 minutes. Assume the cooling process obeys Newton’s Law of Cooling.
(i) Using the two temperature readings, determine the cooling constant k (per minute) correct to four decimal places.
(ii) How long, measured from the instant the coffee was placed in the room, will it take for the temperature of the coffee to reach 40∘C? Give your answer to the nearest minute.