- #1
Psyguy22
- 62
- 0
1 the problem and all known variables.
A person is murdered in a room with a temperature of 20 deg C. At the time the body is discovered, the body temp is 32 deg C and is decreasing at an instantaneous rate of .1 deg C/minute. How long ago was the murder commited?
2. Related equations.
Normal body temp is 37 deg C
Y(t)=T+Ae^(-kt) where y(t) is temp at a given time, T is the room temp, and A and K are constants related to cooling.
3 attempt at solution.
So my teacher gae the hint to have t=0 be the time the body was discovered. So you'd get 32 (y(0)) = 20+A ((e^0=1). I got that A=12. So plug that back into the eq. And because the body temp decreases at .1 deg C/minute, K would equal .1. So then I solve y(t) for 37 and I get -3.7 which if it were in hours, that answer would make sense. But since k was in minutes, I figured my answer was too so then I converted k to hours revised my answer and got -207 which is a really long time. I'm confused in where I went wrong.
A person is murdered in a room with a temperature of 20 deg C. At the time the body is discovered, the body temp is 32 deg C and is decreasing at an instantaneous rate of .1 deg C/minute. How long ago was the murder commited?
2. Related equations.
Normal body temp is 37 deg C
Y(t)=T+Ae^(-kt) where y(t) is temp at a given time, T is the room temp, and A and K are constants related to cooling.
3 attempt at solution.
So my teacher gae the hint to have t=0 be the time the body was discovered. So you'd get 32 (y(0)) = 20+A ((e^0=1). I got that A=12. So plug that back into the eq. And because the body temp decreases at .1 deg C/minute, K would equal .1. So then I solve y(t) for 37 and I get -3.7 which if it were in hours, that answer would make sense. But since k was in minutes, I figured my answer was too so then I converted k to hours revised my answer and got -207 which is a really long time. I'm confused in where I went wrong.