New answers tagged

0

The answer to this relies on knowing about the extended solutions for the Schwarzschild solution, namely the Kruskal solution. In this solution, there is not just a black hole, but a pair of a black hole and a white hole. Particles move from the white hole in the distant past, and then eventually fall into the black hole. Therefore, the time-reversed ...


3

For an irreversible expansion or compression, let $P_B(t)$ represent the gas pressure on the portion of its boundary where the work is being done, and let $T_B(t)$ represent represent the gas temperature on the portion of the boundary where heat transfer is taking place, with $t$ representing the time during the irreversible change. If the change is ...


1

I think the answer to the question is basically that not only the flow itself cannot be reversed, but more generally, and maybe more clearly, there is no flow which could take you in the reverse way, no matter what is the suggested path. Since there is a decreasing function characterizing any flow, then any RG flow violating this decreasing fashion is ...


0

Suppose that a system is subjected to an irreversible process between two thermodynamic equilibrium states. To determine the change in entropy of the system $\Delta S$ between these two equilibrium states, you execute the following sequence of steps: Forget about the irreversible process path. It cannot be used to determine the change in entropy. Focus ...


0

What I try to say, is that it makes equally sense if a ball rolls down of tray or up (without friction) in a newtonian system. The "proces" is then reversible. In thermodynamics a proces will only go one way in a given situation therefore irreversible. – Hamid Mohammad 18 hours ago When you think of a ball rolling up or down a hill it is easy to ...


0

You have to be a bit careful about what you mean when you ask about Newtonian mechanics being reversible or not. As stated in one of the comments newtons mechanics is only a set of rules that tell you how objects accelerate if they are subject to some sets of forces. It does not necessarily tell you the nature of these forces of where they come from. To ...


0

The state equation says: P V = R T For an isothermal process, T is constant by definition R is a physical constant For an expansion process V is increasing So, P must necessarily be decreasing for the gas within the system Assuming a constant piston area of A, the force on the piston is: F (on piston from internal gas) = P (internal gas) A ...



Top 50 recent answers are included