HOW DO I DO THIS QUESTION BY USING C++?

Question

1.00/5 (4 votes)

See more:

The medical examiner arrives at the crime scene and takes the temperature, T_i, of the deceased. An hour later the medical examiner again takes the temperature T_f of the deceased. The examiner notices that the thermostat in the room is set for a constant T_a temperature. From this data and Newton's Law of Cooling, design, write, compile, run and debug a program that takes in (use cin) temperatures T_i, T_f and T_a in degrees Fahrenheit from the user and displays those temperatures, constant k, and the approximate length of time t_h in hours between the death of the individual and the arrival of the examiner (assume the individual's body temperature was T_d = 98.6 degrees Fahrenheit at the time of death).

Step 1: Determine constant k from: k = (-log((T_f - T_a)/(T_i - T_a)))/1.0
Step 2: Determine t_h in hours from: t_h = (-log((T_i - T_a)/(T_d - T_a)))/k
Step 3: Print out the value of t_h in hours.

[EDIT - OP code from comment]
okay, so I did my best but the answer it gives me don't seem like a right answer..... Im not sure if I did something wrong

C++

#include<iostream>
#include<iomanip>
#include<cmath>

using namespace std;

int main()
{

double T_i,T_f,T_a,k,T_h;
const double T_d = 98.6;

cout<<	 "Determine length of time t_h in hours between the death of the individual and the arrival of the examiner "<<endl<<endl;

cout<< "Enter the value of T_i: ";
cin>> T_i;
cout<< "Enter the value of T_f: ";
cin>> T_f;
cout<< "Enter the value of T_a: ";
cin>> T_a;
k = (-log((T_f - T_a)/(T_i - T_a)))/1.0;
T_h = (-log((T_i - T_a)/(T_d - T_a)))/k;

cout<< setiosflags(ios::fixed)
<< setiosflags(ios::showpoint)
<< setprecision(4)
<< "time between the death of the individual and the arrival of the examiner:"<<T_h<< "hours"<<endl;


return 0;


}

Posted 31-Jan-16 9:51am

Member 12298677

Updated 1-Feb-16 3:45am

CHill60

v2

Add a Solution

Comments

CHill60 31-Jan-16 16:17pm

~~Of course, if you react with nothing but a down vote then that will be at least one less member prepared to help further down the line.~~ Apologies - it appears it wasn't you. However please see the following questions...
What have you actually tried, where are you stuck, what went wrong?

Andreas Gieriet 31-Jan-16 17:00pm

What's the problem exactly?
You read in three values (cin >> t_f, etc.), calculate from these values the value of k (#include <cmath>, use the proper "log" function, etc.), then the value of t_h, and finally print t_h (cout << t_h, etc.).
So, again: what's the problem? Choose the right types? choose the right logarithm? C++ as such (includes, namespaces, main function, ...)?
Do you have test data to check against?
Cheers
Andi

[no name] 1-Feb-16 10:10am

k = (-log((T_f - T_a)/(T_i - T_a)))/1.0;

Is " / 1.0" (divide by one) a typo or is it really not necessary?
[ok, seems to be the Delta t]

Have look here: Newton's Law of Cooling -- EndMemo[^]

Stefan_Lang 5-Feb-16 5:13am

Unfortunately the 'k' value calculated by the formula above uses hours and Fahrenheit rather than seconds and Celsius. Therefore you can't use it with the calculator on that site to cross-check a given result.

P.S.: the '/1.0' part of the formula really reads '/1.0h' because 1h is the time difference between the measurements. To convert this to metric, you'd need to divide by 3600s instead.

[no name] 5-Feb-16 7:08am

Thank you for Feedback. Fahrenheit instead of Celsius: That was also my first thought. But if you have a closer look to the formula you will recognize, that the formula works for both :)

Stefan_Lang 5-Feb-16 7:24am

Indeed it does, I noticed that k isn't dependend on the temparature unit at all. But its value gets scaled due to using hours rather than seconds. So in the calculator you need to make sure that you are using the same time unit for the time difference as you used for determining k.

Stefan_Lang 5-Feb-16 4:58am

The results I get from that code look fine to me. What inputs did you use and what result did you get that you think is not correct? Maybe you're interpreting it incorrectly.

P.S.: I used the example on the site linked above to verify a slightly modified version of your formulas in a Google sheet, here:
https://docs.google.com/spreadsheets/d/1qUEUekfUx-lNbe8O-alXcg5GKkdTCjaOApnJ06PJA8Q/pubhtml

I also included a function plot to visualize the results. Everything looks fine to me, and your program appears to be doing the exact same thing (except for a smaller time interval etween measurements).

1 solution

Add a Solution

Add your solution here

Treat my content as plain text, not as HTML

Preview 0

…

Existing Members

Sign in to your account

...or Join us

Download, Vote, Comment, Publish.

Your Email
Password
Forgot your password?

Your Email
This email is in use. Do you need your password?
Optional Password

I have read and agree to the Terms of Service and Privacy Policy
Please subscribe me to the CodeProject newsletters

When answering a question please:

Read the question carefully.
Understand that English isn't everyone's first language so be lenient of bad spelling and grammar.
If a question is poorly phrased then either ask for clarification, ignore it, or edit the question and fix the problem. Insults are not welcome.
Don't tell someone to read the manual. Chances are they have and don't get it. Provide an answer or move on to the next question.

Let's work to help developers, not make them feel stupid.

This content, along with any associated source code and files, is licensed under The Code Project Open License (CPOL)

CHill60 · Answer 1 · 2016-01-31T09:52:00

Solution 1

This is homework.
We don't do your homework for you.
Why? Because it doesn't help you.

Give it a try.
Follow your course notes.

When you get stuck, then post a question that includes the code you have tried and details of where you are stuck.

We are more than happy to help ... but only if you try

Posted 31-Jan-16 9:52am

CHill60

Comments

Dave Kreskowiak 31-Jan-16 16:30pm

Whoever hit you with a 1 vote is someone who's been around for quite a while. They hit you as hard as I can.

CHill60 31-Jan-16 16:37pm

Cheers!
I've looked again and apologised to the OP.
Thank you for the balancing vote.
I'm more concerned about whoever it is that is randomly downvoting (again!) ... I'm happy to be corrected when I'm wrong, and appreciate corrective comments, but there is someone out there being silly at the moment

Andreas Gieriet 31-Jan-16 16:55pm

My 5!
Cheers
Andi

Member 12298677 31-Jan-16 20:22pm

okay, so I did my best but the answer it gives me don't seem like a right answer..... Im not sure if I did something wrong
#include<iostream>
#include<iomanip>
#include<cmath>

using namespace std;

int main()
{

double T_i,T_f,T_a,k,T_h;
const double T_d = 98.6;

cout<< "Determine length of time t_h in hours between the death of the individual and the arrival of the examiner "<<endl<<endl;

cout<< "Enter the value of T_i: ";
cin>> T_i;
cout<< "Enter the value of T_f: ";
cin>> T_f;
cout<< "Enter the value of T_a: ";
cin>> T_a;
k = (-log((T_f - T_a)/(T_i - T_a)))/1.0
;T_h = (-log((T_i - T_a)/(T_d - T_a)))/k

;cout<< setiosflags(ios::fixed)
<< setiosflags(ios::showpoint)
<< setprecision(4)
<< "time between the death of the individual and the arrival of the examiner:"<<T_h<< "hours"<<endl;

return 0;

}

CHill60 1-Feb-16 9:47am

So your next step is to debug the code ... which of the answers that you arrived at do you think is wrong? Have you checked your results using a calculator?

Philippe Mori 1-Feb-16 13:10pm

Don't post code in a reply. It is unreadable. Update your question instead.

chandanadhikari 1-Feb-16 0:23am

5!
cheers