Thermodynamics - Use conservation of energy to answer these questions....

[lc99]

Homework Statement

Homework Equations

The Attempt at a Solution

I understand how they got Q1 and Q2 for the first two columns, but how am i suppose to find Q1 and Q1 for the 3rd and 4th event?

Isn't it just 0? Cause it seems like the temperatures just stayed constant. I'm not entirely sure what the worksheet is asking me to do.

I think this may relate to carnot engine and heat engines that are reversible

 

[Chestermiller]

Homework Statement

View attachment 224684

Homework Equations

The Attempt at a Solution

I understand how they got Q1 and Q2 for the first two columns, but how am i suppose to find Q1 and Q1 for the 3rd and 4th event?

Isn't it just 0? Cause it seems like the temperatures just stayed constant. I'm not entirely sure what the worksheet is asking me to do.

I think this may relate to carnot engine and heat engines that are reversible

Energy is being generated by fusion within the sun, so its temperature is not decreasing. What are your answers now?

What are your assessments of the changes in entropy?

 

[dRic2]

Event 2 is impossible for sure because even if it doesn't break conservation's law heat can't go from a colder object to an hotter one. I don't understand event 3 and 4.

 

[Chestermiller]

Event 2 is impossible for sure because even if it doesn't break conservation's law heat can't go from a colder object to an hotter one. I don't understand event 3 and 4.

By the same rationale, what is your assessment of whether Event 3 or Event 4 is possible?

 

[dRic2]

By the same rationale, what is your assessment of whether Event 3 or Event 4 is possible?

I'm not the OP so I don't know exactly what the question is... it seems nonsense to me.

 

[Chestermiller]

I'm not the OP so I don't know exactly what the question is... it seems nonsense to me.

Oops. Sorry, I mistook you for the OP.

 

[dRic2]

Never mind, It happens to me as well

 

[lc99]

By the same rationale, what is your assessment of whether Event 3 or Event 4 is possible?

Kinda got some insight from the above poster. I think event 3 is is possible since heat is moving from hot object to cold object.
Event 4 is impossible because Earth can transfer heat to the sun if it is colder than the sun.

 

[lc99]

Event 2 is impossible for sure because even if it doesn't break conservation's law heat can't go from a colder object to an hotter one. I don't understand event 3 and 4.

Oh i get it. Cause cooling doesn't give heat?

 

[tnich]

I understand how they got Q1 and Q2 for the first two columns, but how am i suppose to find Q1 and Q1 for the 3rd and 4th event?

"Sun(1) transfers 58MJ of thermal energy to earth(2)." What about that is unclear?

 

[lc99]

"Sun(1) transfers 58MJ of thermal energy to earth(2)." What about that is unclear?

I'm more confused with the temperatures that they listed in the chart. Why would they use the same numbers for final temp?

 

[tnich]

I'm more confused with the temperatures that they listed in the chart. Why would they use the same numbers for final temp?

The heat capacity of Earth's atmosphere is about 1X10⁷J/m²/°C, that is, for each square meter of Earth's surface, it takes 1X10⁷J to change the temperature of the atmosphere above it by 1°C. The radius of the Earth is about 6.4X10⁶m. So how much does 57MJ change the temperature of the atmosphere? (Notice that we are just talking about the atmosphere here, without even considering anything below the surface of the planet.)

 

[Chestermiller]

The heat capacity of Earth's atmosphere is about 1X10⁷J/m²/°C, that is, for each square meter of Earth's surface, it takes 1X10⁷J to change the temperature of the atmosphere above it by 1°C. The radius of the Earth is about 6.4X10⁶m. So how much does 57MJ change the temperature of the atmosphere? (Notice that we are just talking about the atmosphere here, without even considering anything below the surface of the planet.)

What about the heat re- radiated to space. This is pretty much in balance with the heat received from the sun.

 

[tnich]

What about the heat re- radiated to space. This is pretty much in balance with the heat received from the sun.

That is true on average, but daytime temperatures are several degrees higher than nighttime temperatures, so there is a transient warming effect of the sun. My point was to make clear the order of magnitude of the temperature change that 57MJ of energy would cause.