# Tagged Questions

Covers the study of (mostly homogeneous) macroscopic systems from a heat/energy/entropy point of view. Maybe combine with [tag:statistical-mechanics].

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### energy efficiency - dryer vs hang+dehumidifer

When I have wet clothes coming out of the washing machine, I can either tumble-dry them in an electric clothes-dryer, or I can hang them to dry. But I can only hang them in a basement. The basement ...
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### Temperature of planets without atmosphere

I am wondering how come a planet without atmoshhere loses heat in space when the space around it is a vacuum. In my understanding for one object to lose heat it must have contact with another object/...
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### Does stopping the same bike and rider at the same velocity with the front brake require less energy than the back brake?

It's the same body made by the rider and the bike moving at the same speed. So, even though braking on the front/back alters the normal forces on the opposite wheels thus creating more friction with ...
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### Why do we ignore rotational energy in monatomic gases? [duplicate]

I understand that the average energy of each degree of freedom in a thermodynamic system is $\frac12kT$. And so, for an ideal monatomic gas, there are three degrees of freedom associated with the ...
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### Find an expression for S(T,x) from tension and specific heat

I'm working on a problem from a Statistical Mechanics lecture series online, and on the homework, I hit a bump in this problem. Here is the problem set, and I'm asking about #1.c. Short version, we ...
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### How do I calculate the change in water temperature as a function of depth?

Let's say I have ground water at a depth of $3000m$ at $50^{o}C$. If I now pump this water up to the surface, the water pressure decreases from the $\pm 300 atm$ at that depth to $1 atm$ at the ...
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### Finding the Enthalpy of an Ideal Gas given internal energy

I am trying to find a formula for tying things up. Given an ideal gas like helium or nitrogen gas (diatomic) how can I find its enthalpy simply given internal energy? I remember it was once taught in ...
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### Rapid/ Slow Expansion in Gases

How is rapid expansion of gases different from slow expansion?
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### Can I measure the volume of a locked room by pumping gas through keyhole and measuring its entropy?

Suppose that I have a locked room and a keyhole in the door and I want to measure the room's volume. Suppose also that I have some "magical" "artificial" inert gas A that doesn't interact with ...
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### How does the heat death looks like from inside the system?

As this answer points out, any human would first freeze rather than experience the heat death. However, assuming hypothetically that we could make some robot live at such low temperature (or even ...
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### Understanding the Carnot cycle

My textbook explains the Carnot cycle as follows: Heat is added to the boiler, where the steam inside expands isothermally at high temperature (T(High))--(both valves closed). The intake valve is ...
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### Water enclosed in a vessel

Suppose I am taking water in a glass or metal or even something else. It s air tight and (so it is water tight). Now imagine, if I keep it heating and none of its molecule escapes from it, what am I ...
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### Two glass bottles of water warming by different temperatures

A friend posed a question to me yesterday: if I have two glasses of 60 F water, would they heat at a different rate if one were in a 70 F room and one were in a 90 F room. Myself having some ...
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### Should the weaker of two air conditions be switched off?

We have two airconditioning systems in the office. For the sake of this question, let us assume the following current conditions: AC1 (old) outputs air of 26°C AC2 (new) outputs air of 18°C Office ...
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### Distinguishing Isentropic Process; Are all things in an insulated cylinder considered reversible adiabatic?

How much work is necessary to compress air in an insulated cylinder from 0.20m^3 to 0.01m^3. Use T1 = 20C and P1 = 100 kPa. I don't need to solution or the answer. I already have it. But I think ...
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### How much a juice maker increases the temperature of the product?

Recently I asked on skeptics if cold pressed juice is higher in nutrients than one from centrifugal juicer and one of the claims is that the centrifugal juicer heats the juice enough to destroy ...
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### Gough-Joule effect in rubber band

When a stretched rubber band is heated, surprisingly, its tension will increase. What is the physics behind this?! Another thing. The Entropic spring model says, for a good specimen, that the ...
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### Measuring variation of saturated vapour pressure with temperature

Is it possible to measure variation of saturated vapour pressure of water with time.I just hesitate about it.My suggested procedure which is incomplete is given below Procedure that I would like to ...
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### steady state and thermodynamic equilibrium

What is the difference between a system being in a steady state and thermodynamic equilibrium ? Can a system be in steady state but not in thermodynamic equilibrium and vice-versa?
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### Efficiency of an Internal Combustion Engine

This question is about How correct are those comments on efficiecy of internal combustion(IC) engines which calcuate it using 2nd law of thermodynamics.The maximum efficiency of a heat engine can be ...
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### Will Neil Armstrong's moon boot marks really last for thousands of years?

This question concerns the residual heat (if any) contained within the Earth's moon. At the time of the Apollo moon landings, it was widely reported that the boot marks left by the astronauts would ...
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### Is a larger, heated space easier or harder to ventilate if the heat source and ventilation are the same?

Imagine a well insulated room with a heat source inside. The room has two vents, which each have a fan. Cool air is drawn into the room through one vent, and warm air is pushed out the other vent. ...
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### Is a body of gas cooler in its upper portion as a result of gravity? [closed]

I read an article a couple of hours ago named Hydrostatic Lapse which makes the case for a phenomenon that I thought was well and truly confirmed; that gravity is responsible for the cooling of gas ...
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### Heat loss during evaporation of a liquid boiling due to Bernoulli effect

this is my first post here. I watched this video https://www.youtube.com/watch?v=h5wQoA15OnQ and at 51 seconds it describes Bernoulli's effect of a drop in pressure resulting from an increased ...
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### How accurate is the Callendar-Van Dusen equation?

... over 0 degC to 100 degC? The equation itself can be found here I can do a very accurate one point calibration of a 1/10 DIN PT100 sensor at 0 degC. If I use the equation to correct for non-linear ...