# Temperature

• May 2nd 2009, 05:25 PM
cammywhite
Temperature
The late Mac the Knife is found at midnight with a body temperature of 90 degrees F, in a room where the temperature is 70.
At 1 a.m. he has cooled to 80 degrees.

When was he killed? Why?

Can this equation get me to the answer?

$89 = 70 +20e^{-0.01t}$
• May 2nd 2009, 08:24 PM
warmonk102
Is that all that was given to you? The question seems to be very confusing. Your equation is right but -.01 shouldn't be there btw, you need to use Newton's law of cooling which states that if u is the object then the rate at which it cools is

du/dt = -k(u - T)

-k = constant

T = ambient temperature
• May 3rd 2009, 02:11 AM
mr fantastic
Quote:

Originally Posted by cammywhite
The late Mac the Knife is found at midnight with a body temperature of 90 degrees F, in a room where the temperature is 70.
At 1 a.m. he has cooled to 80 degrees.

When was he killed? Why?

Can this equation get me to the answer?

$89 = 70 +20e^{-0.01t}$

You need to solve the differential equation (Newton's law of Cooling) given in post #2. Let t = 0 correspond to midnight. Then the boundary conditions for this differential equation are T = 90 degrees F at t = 0 and T = 80 degrees F at t = 1.

You need to find the value of t (it will be negative) when T = 98.9 degrees F (normal temperature of living person).