Question

28.
A cup of tea cools from 65.5°C to 62.5°C in one minute in a
room of 22.5°C. How long will the same cup of tea take to
cool from 46.5°C to 40.5°C in the same room. (Choose the
nearest value in min.)
(a) 1
(b) 2
(c) 3
(d) 4​

Answer 1

Answer:

According to Newton's Law of Cooling,

        Q1-Q2/t=k(Q1+Q2/2-T)

        65.5-62.5/60=k(65.5+62.5/2-22.5)

                3/60=k(64-22.5)

                1/20=41.5k

                 1=830k-----(1)

          Q1-Q2/t=k(Q1+Q2/2-T)

           46.5-40.5/t=k(46.5+40.5/2-22.5)

                     6/t=k(87/2-22.5)

                     6/t=k(43.5-22.5)

                     6/t=21k

                        1=21kt/6-----(2)

Comparing the two equations,

                   830k=21kt/6

                     830=21t/6

                   4980=21t

    therefore, t=4980/21=237.14 s

                                        =3.95 min ≈ 4 min

PLEASE MARK ME AS BRAINLIEST IF IT HELPS YOU