Question

Jane makes coffee with water from an urn which is at a temperature of 100 deg C.
Jane carries a thermometer with her at all times and notes that 7 minutes later her coffee has cooled to 70 deg C.
The room is not air-conditioned, and is 30 deg C.
Suppose the temperature Tfollows Newton’s Law of Cooling (note that this is slightly different to, but equivalent to, the form given in lectures):
T(t)=Ta+CKt∕7
where tis the number of minutes after the coffee was made.

(a) Find the value of Ta, C and the exact value of K (as a fraction)

(b) Find the coffees temperature after ten minutes

(c) After how many minutes has the coffees temperature dropped to 60 degress? (minutes).

Answer 1

bynaoton lau ot cooling |うJK=0.01994 -07940 given Ta -3016 at t=0→7-100 6l 4104 ern becomes atT-60 60-30-eO-079944-) -KCT) 카0 FK -TO ะเ0.59 921 min