## Thermodynamics B/C

mjcox2000
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State: VA

### Re: Thermodynamics B/C

wec01 wrote:
mjcox2000 wrote:
UTF-8 U+6211 U+662F wrote: I'm confused how the reservoirs could reach equilibrium? The Carnot cycle assumes that the reservoirs will never change temperature.
The Carnot cycle doesn’t require constant-temperature reservoirs.
The Carnot efficiency equation predicts the instantaneous efficiency. Try integrating.
1. 252 K
2. 5920 J
3. 2880 J
4. 48.6 %
Correct on parts 1, 2, and 3.
It should be 51.4% — I assume you found the percentage of wasted energy, not usable energy.
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wec01
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State: VA

### Re: Thermodynamics B/C

Suppose you had a cylinder with a piston in it. Describe how you would cause the system to undergo:
2. isothermal expansion
3. isobaric expansion
2019 Division C Nationals Medals:
4th place Fossils
5th place Sounds of Music
2nd place Thermodynamics

mjcox2000
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Posts: 121
Joined: May 9th, 2014, 3:34 am
State: VA

### Re: Thermodynamics B/C

wec01 wrote:Suppose you had a cylinder with a piston in it. Describe how you would cause the system to undergo:
2. isothermal expansion
3. isobaric expansion
1. Quickly pull on the piston
2. Submerge the cylinder in a constant-temperature water bath and slowly pull on the piston
3. Heat the cylinder and don’t touch the piston
MIT ‘23
TJHSST ‘19
Longfellow MS

See my user page for nationals medals and event supervising experience.

wec01
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Posts: 220
Joined: February 22nd, 2019, 4:02 pm
State: VA

### Re: Thermodynamics B/C

mjcox2000 wrote:
wec01 wrote:Suppose you had a cylinder with a piston in it. Describe how you would cause the system to undergo:
2. isothermal expansion
3. isobaric expansion
1. Quickly pull on the piston
2. Submerge the cylinder in a constant-temperature water bath and slowly pull on the piston
3. Heat the cylinder and don’t touch the piston
2019 Division C Nationals Medals:
4th place Fossils
5th place Sounds of Music
2nd place Thermodynamics

mjcox2000
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Posts: 121
Joined: May 9th, 2014, 3:34 am
State: VA

### Re: Thermodynamics B/C

A sample of air starts at STP. Then, a sound source emitting a 10kHz sine wave is placed in the sample of air. At a certain point P at a given distance from the sound source, the RMS sound pressure level is 100 dB. Assuming air behaves adiabatically when sound travels through it and there are no frictional losses, what is the minimum and maximum temperature at point P?
MIT ‘23
TJHSST ‘19
Longfellow MS

See my user page for nationals medals and event supervising experience.

wec01
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Posts: 220
Joined: February 22nd, 2019, 4:02 pm
State: VA

### Re: Thermodynamics B/C

mjcox2000 wrote:A sample of air starts at STP. Then, a sound source emitting a 10kHz sine wave is placed in the sample of air. At a certain point P at a given distance from the sound source, the RMS sound pressure level is 100 dB. Assuming air behaves adiabatically when sound travels through it and there are no frictional losses, what is the minimum and maximum temperature at point P?
$\pm 9.2 * 10^{-3} ^{\circ} C$
2019 Division C Nationals Medals:
4th place Fossils
5th place Sounds of Music
2nd place Thermodynamics

wec01
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Posts: 220
Joined: February 22nd, 2019, 4:02 pm
State: VA

### Re: Thermodynamics B/C

wec01 wrote:
mjcox2000 wrote:A sample of air starts at STP. Then, a sound source emitting a 10kHz sine wave is placed in the sample of air. At a certain point P at a given distance from the sound source, the RMS sound pressure level is 100 dB. Assuming air behaves adiabatically when sound travels through it and there are no frictional losses, what is the minimum and maximum temperature at point P?
$\pm 9.2 * 10^{-3} ^{\circ} C$
Oops, I see an error in my work; working on fixing it
2019 Division C Nationals Medals:
4th place Fossils
5th place Sounds of Music
2nd place Thermodynamics

wec01
Member
Posts: 220
Joined: February 22nd, 2019, 4:02 pm
State: VA

### Re: Thermodynamics B/C

wec01 wrote:
wec01 wrote:
mjcox2000 wrote:A sample of air starts at STP. Then, a sound source emitting a 10kHz sine wave is placed in the sample of air. At a certain point P at a given distance from the sound source, the RMS sound pressure level is 100 dB. Assuming air behaves adiabatically when sound travels through it and there are no frictional losses, what is the minimum and maximum temperature at point P?
$\pm 9.2 * 10^{-3} ^{\circ} C$
Oops, I see an error in my work; working on fixing it
$\pm 7.6 * 10^{-3} ^{\circ} C$
2019 Division C Nationals Medals:
4th place Fossils
5th place Sounds of Music
2nd place Thermodynamics

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