Calculate the power temperature

AI Thread Summary
The discussion revolves around calculating the power generated by humans from a typical daily diet of 2000 kcal and its effect on room temperature for 250 people in a 15,000 m³ space over an hour. The initial calculation yielded a power output of 2.3 W, which was later corrected, noting that the time should reflect a full day rather than an hour, significantly increasing the power value. The specific heat capacity of air is also mentioned, but the user struggles with applying the relevant equations to find the temperature increase. Clarifications on the definitions of power and energy units are provided, emphasizing the need for accurate calculations. The conversation highlights the importance of understanding the relationship between energy, power, and temperature changes in a given volume.
JQ10
Messages
3
Reaction score
0
Edit: Topic title should read power and temperature

Homework Statement



Humans convert most of a 2000 kcal typical daily diet into heat. Calculate the power. What is the increase of temperature in a room with a volume of 15000 m^3 filled with 250 people over a 60 minute period?

Note: Power is defined as energy/time.
1kcal = 4.186kJ.
density of air = 1.29kg/m^3
molar mass of air = 29g
Treat air as a diatomic gas


Homework Equations



C = change in internal energy/ number of moles * change in temperature = f/2*R



The Attempt at a Solution



60 * 60 = 3600

2000 * 4.186 = 8372kJ/3600s = 2.3kJ/s = 2.3W

Specific Heat Capacity = 5/2 * R = 5/2 * 8.31 = 20.8 kJ/moleK

I'm really struggling with where to take it from there. I'd guess you would either use change in internal energy/ number of moles * change in temperature or use average kinetic energy = 5/2kT = 1/2mv^2rms but I'm not sure how to calculate the relevant data for either plus that doesn't use all the information given.
 
Last edited:
Physics news on Phys.org
JQ10 said:
Humans convert most of a 2000 kcal typical daily diet into heat.
60 * 60 = 3600
2000 * 4.186 = 8372kJ/3600s = 2.3kJ/s = 2.3W

I have not played with attempting the find the specific heat of air before so I'll let someone else help you there. I can tell you that the power involved is not 2.3 W because there are not 3600 seconds in a day. Note that the problem said "daily." And a watt is not equal to kJ/s but J/s. Due to those two errors, your power is small by an order of magnitude.
 
Thank you for the help.
 
Thread 'Struggling to make relation between elastic force and height'
Hello guys this is what I tried so far. I used the UTS to calculate the force it needs when the rope tears. My idea was to make a relationship/ function that would give me the force depending on height. Yeah i couldnt find a way to solve it. I also thought about how I could use hooks law (how it was given to me in my script) with the thought of instead of having two part of a rope id have one singular rope from the middle to the top where I could find the difference in height. But the...
Thread 'Voltmeter readings for this circuit with switches'
TL;DR Summary: I would like to know the voltmeter readings on the two resistors separately in the picture in the following cases , When one of the keys is closed When both of them are opened (Knowing that the battery has negligible internal resistance) My thoughts for the first case , one of them must be 12 volt while the other is 0 The second case we'll I think both voltmeter readings should be 12 volt since they are both parallel to the battery and they involve the key within what the...
Back
Top