S.O.S. Mathematics CyberBoard

Your Resource for mathematics help on the web!
It is currently Wed, 3 Sep 2014 03:05:11 UTC

All times are UTC [ DST ]

Post new topic Reply to topic  [ 2 posts ] 
Author Message
PostPosted: Wed, 9 May 2012 15:15:35 UTC 
S.O.S. Newbie

Joined: Wed, 9 May 2012 15:07:45 UTC
Posts: 1
By Newton’s law of cooling the temperature T of a cooling object as a function of time is

TO - initial temperature,
T1 is ambient temperature (meaning the temperature outside the cooling object)
k is constant

-32C was the te,perature when electricity was cut off and heating of a house stopped working. After 2 hours from the power cut the inside temperature was measured to be 19,2 C, and after that the following measurements were done:

2,5 hours: 18,3 oC
3,0 hours: 17,5 oC
3,5 hours: 16,6 oC
4,0 hours: 15,8 oC
4,5 hours: 14,9 oC
5,0 hours: 14,2 oC

Supposing Newton’s cooling law to be valid in this case,


T0 initial temperature (which is the temperature at moment t=0 when the power was cut off). Try also to predict when the inside temperature will be dropped below zero.


my attempt:


51.2 (T0-32)e-k(2)
46.2 (T0-32)e-k(5)

1.11 e2,5k
k= 0.041103894
k= ln(1.11)/2.5

Substitude k into the first equation


and now ?????????????

PostPosted: Thu, 10 May 2012 19:33:44 UTC 
S.O.S. Newbie

Joined: Thu, 10 May 2012 10:10:29 UTC
Posts: 1
According to your post the starting temperature is -32C (MINUS 32 C) and after 2 hours 19.2C (PLUS 19.2C). The rest of the temperatures are also positive. Either change the stating temperature to a 32C or the rest of the temperatures to negative ones.

Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 2 posts ] 

All times are UTC [ DST ]

Who is online

Users browsing this forum: No registered users

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  
Contact Us | S.O.S. Mathematics Homepage
Privacy Statement | Search the "old" CyberBoard

users online during the last hour
Powered by phpBB © 2001, 2005-2011 phpBB Group.
Copyright © 1999-2013 MathMedics, LLC. All rights reserved.
Math Medics, LLC. - P.O. Box 12395 - El Paso TX 79913 - USA