Thermodynamics: Internal Energy of a Gas

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Homework Help Overview

The problem involves calculating the internal energy of a monatomic gas, specifically helium, contained in a specified volume and under a given pressure. The goal is to determine the time required for a specific engine to produce energy equivalent to the internal energy of the gas.

Discussion Character

  • Exploratory, Mathematical reasoning, Problem interpretation

Approaches and Questions Raised

  • Participants discuss using the ideal gas law and the relationship between internal energy and temperature. There are attempts to calculate the internal energy and relate power to energy and time.

Discussion Status

Some participants have provided calculations for internal energy and power, while others are questioning their results and the relationship between power and time. There appears to be a mix of interpretations regarding the calculations, with some participants revising their answers based on feedback.

Contextual Notes

Participants are working under the constraints of homework guidelines, which may limit the information they can use or the methods they can apply. There is also a focus on ensuring the calculations align with the physical principles involved.

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Homework Statement


Helium (He), a monatomic gas, fills a 0.010-m^3 container. The pressure of the gas is 6.2 multiplied by 10^5 Pa. How long would a 0.38-hp engine have to run (1 hp = 746 W) to produce an amount of energy equal to the internal energy of this gas?



Homework Equations




Equations: DU = Q + W , Possibly PV = nRT?, Possibly DU = 3/2 n R T ?

The Attempt at a Solution


No idea how to go about doing this.
 
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Use PV = nRT and U = 3/2nRTtherefore U=3/2(PV).R.
 
Last edited:
So using that, I get U = 9300J,
P= 290.32 W,
So how do I find the time?
Thanks.
 
Do you know how power and energy are related to each other?

Or, more simply, what is power?
 
Power = work / time
I substituted in, got 23 seconds, and that is not the right answer...
am I doing something wrong?
 
My power is 283.48W,
which gives t=32.8 s.
 
I redid it and I got 32.08. I think I missed a decimal?
Thanks for the help... i'll try that.

EDIT: Yup it worked! Thanks very much :)
 

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