Question

4. (7 + 4 pts) A cup of hot chocolate has temperature 80°C in a room kept at 20°C. After half an hour the hot chocolate cools to 60°C. (a) What is the temperature of the chocolate after another half hour? ANSWER: (b) When will the chocolate have cooled to 40°C? ANSWER:

Answer 1

ET DIST so KODAD ussing, Newton law of law of cool cooling formula T(t) = TS+ (to - Ts) ekt Gives, Tg-80 ; To=80°c T(t)= 80+ (80-20) ě kt TIH) = 20+ 60 e-kt

at t=% Tit) = 60 >> K/2. 60= 20+ 60 40 -K/2 -) § 2 dlm lék) G² - 9 for no thee half hour i e t=1 TIE) 20+ 60 .kx| = 20+ box 4 glo a 20+ 3 140 3 T(t) = 46-66667 Tit) = 40° t-l - 4o- 20+ 60 t 20 60 non (a)t

13347556| 글 = () ink)= - 1ml m) t= In () 14 -) hys