# What is Thermodinamic: Definition and 17 Discussions

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1. ### I Kinetic equation of gases: time between collisions instead of time of colission?

I understand everything except why do we use time between collisions instead of time of colission?
2. ### I try to solve a thermodynamics problem on heat transfer

I have some doubts about a thermodynamics exercise I did-I'll write down the text and show how I tried to solve it to see if I reasoned it out right. In a container of thermal capacity ##C## containing ##1.0 kg## of ice at a temperature of ##-4.0 °C##, a mass of ##3.0 kg## of water is poured...
3. ### I Comparing Spacetime and Thermodynamic State Space Manifolds

Hi, I don't know if it is the right place to ask for the following: I was thinking about the difference between the notion of spacetime as 4D Lorentzian manifold and the thermodynamic state space. To me the spacetime as manifold makes sense from an 'intrinsic' point of view (let me say all the...
4. ### Engineering Thermal expansion coefficient calculation — where is my mistake?

Hello everyone, Once I got through the VDW state equation I came to the expression of the thermal expansion coefficient. When I place the values I get an illogical answer. Is there a problem with the units? (Please ignore the values) Thanks. This is the unit equation I get to and get stuck:
5. ### The second law of the thermodynamics and philosophy

The second law of thermodynamics tells us that the amount of useful energy in an isolated system tends to decrease. Does this imply that mankind will reach a point where it cannot longer use any kind of energy? If so, do we have an estimate of how long it will be necessary for to haven't useful...
6. ### Find the change in the Kinetic energy of an Ideal Gas

Homework Statement Let 3/2kT be the kinetic energy of ideal gas per molecules. T the absolute temperature and N the avogadro number. Answer the following questions : 1) when the volume doubled at constant temperature. How many times the kinetic energy per molecule become greater than before...
7. ### What Is the Entropy Change When Ice Melts in Hot Water?

A closed, well-insulated container is filled with 454 g of water at 94.4 °C. To the hot water, 200 g of water ice at exactly 0 °C is added. The mixture reaches an equilibrium temperature of 41.1 °C. Assume the molar heat capacity is constant and all the processes are at constant pressure. The...
8. ### Can the work of a counterclockwise cycle be positive?

Consider an ideal gas following a thermodynamics cycle, represented on a ##P-V## plane. I read that if the cycle is "travelled" clockwise then ##W_{gas, cycle}>0## so the gas does positive work, while if the cycle is "travelled" counterclockwise then ##W_{gas, cycle}<0## but it seems to me that...
9. ### Thermodynamics -- hydrostatics question

Good afternoon. You are a student of the career of physical I am 'm like someone aids with the second section (II) the following problem because I do not understand much. Thank you very much. Problem: Considering that the effects of pressure variation with height are due only factor hydrostatic...
10. ### Release or absortion of energy on bonds and phase change

I believe I can explain why there is energy needed to break intermoleculares bonds and getting into a gas or liquid, but the other way around confuses me. Bonds have potential energy associated to it, so It's needed work to break the bonds, because we would be trying to move a molecule away from...
11. ### Energy efficiency Gain or Loss? What do you think?

Energy efficiency related question: please help with an anwer to the following: Given a flat electrical coil of known dimentions, this coil is used as an induction coil, laid flat, on top of the cooking surface of an induction cooker. Basically, the induction cooker has a copper braided coil...
12. ### Formula for relating time and heat gained for closed system

This is for work. I need to make a table for a client. What we did: had two different closed systems, only difference is material. We had frozen goods in both containers, the containers were both removed from the cooled surroundings they were in and placed outside. The temperatures were...
13. ### Heat transfer of a hot plastic thread in a cold water bath

Hi, I'll describe my problem more specific. I have a continuous flow of this polymer thread (polystyrene) at 465 °K (190°C sorry I'm metric) that needs cooling down. It passes trough a water bath which is kept at 310°K (35°C). Now i try to calculate the heat exchange into the water, to...
14. ### How can I prove this equation?

Hi! I need to prove that: (∂U/∂V)P = TCV/V For a perfect gas. But I don't know start. Can you help me please?
15. ### Thermodynamic Exercise: Adiabatic Cylinder with Double Chamber and Piston

Hello, my name is Roberto and I am engineering student from Spain. I am a new member in the forum and I don´t know if this is the right site to present me but I want to use this moment to say hello to the comunity. I have a doubt with a thermodinamic exercise.I have an adiabatic cylinder with...
16. ### Calculating Change in Internal Energy for Compressed Air in a Closed System

Homework Statement 10kg of air is compressed in a closed system from an initial temperature of 30° C to a final temperature of 260° C. Given cv = 710 J/kg.K. Calculate the change in internal energy. Homework Equations ΔU = Q - W W = P ΔV Q = m c ΔT P V = m R ΔT The Attempt at a Solution...
17. ### Calculating Final Temperature of Isolated System with Ice and Water

i have an easy problem that i can't solve if you throuth 100g of ice at a tempeture of -15C in a glass with 200g of water at a tempeture of 25C. what it the final tempeture of the system? the system is isolated, no heap can get in neither get out. i try to solve this problem using...