# Questions tagged [dissipation]

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### How much energy is lost per bounce with a tennis ball? [closed]

When a tennis ball bounces it loses some energy. How much energy or height is lost per bounce?
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### Energy dissipation in unitary dynamics

In the context of quantum mechanics it is often (e.g. in several Wikipedia pages, like on Quantum dissipation) stated, that: "If the time evolution of a system is unitary (e.g. always in the ...
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### Solution of a differential equation in physics

In physics when we solve the differential equation, in some cases we get two part of the solution, one is real and another is imaginary. Some cases we consider that the real part have some physical ...
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### Is there a relationship between the frequency of a standing wave on an oscillating string and the half-life of its amplitude as it decays?

I'm asking in the context of an experimental exercise where we used a speaker to create a standing wave on a string with constant tension, then turned off the speaker and allowed the amplitudes to ...
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### Experimental lower bound on the lifetime of a supercurrent?

Nothing is perfect, everything has friction---except in quantum physics, where macroscopic superconductors allow for dissipationless currents. It's an astounding theoretical prediction, and so it is ...
907 views

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### Work done over a closed loop

Is it true that the work done in the motion of a body over a closed loop is zero for every force in nature?
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### Thermodynamics: how does the deformation of partially elastic materials produce heat?

When a perfectly elastic material is deformed, the energy associated with the strain remains stored in the body as elastic potential energy, called strain energy. Upon the removal of the deforming ...
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### How do resistors generate different heat if we make the current fixed and changed the voltage and resistance? Notice the flow of charge is constant

Consider having a circuit which consists of a battery and one resistor. $V = 10$ volts, $R = 5$ ohms, so $I = 2$ Amperes, and $P = 20$ watts. If we double the voltage and resistance, the current ...
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### In Feynman lecture Vol1. chapter12 about friction, $F = μN$ will fail because of the excessive heat generated. Why is that?

$F = μN$ will fail because of the excessive heat generated if the normal force or the speed of motion gets too big. Why is that? "$F = μN$, where μ is called the coefficient of friction (Fig. 12-1)....
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### Examples of non-Hermitian Hamiltonians in open systems?

I have often heard the statement that non-Hermitian Hamiltonians can be used to describe open systems, since the dynamics are non-unitary. However, I have not been able to find any examples of a non-...
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### Damped forced Oscillation with variable external frequency

Consider that we have the following forced vibration with an input frequency $ω(t)$ variable in time. $$m\ddot{x}+c\dot{x}+kx = F_0 \sin{(\omega(t) t)}$$ Assuming that the solution must be a ...
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### Absence of dissipative forces in a reversible process

I can't understand why dissipative forces must be absent during a reversible transformation. Aren't they a way of exchanging heat with ambient? Since the system is allowed to exchange heat with the ...
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### Klein-Gordon/Maxwell Equation: dissipative or dispersive?

In Aspects of Symmetry, Coleman says (p. 185) ''Most of the simple field theories with which we are familiar have the property that all of their non-singular solutions of finite total energy are ...
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### How can dissipative/friction terms be incorporated into a Lagrangian?

I'm trying to find a suitable Lagrangian for a damped harmonic oscillator, a system that satisfies the following equation of motion: $$m \ddot{x} + \gamma \dot{x} + \frac{d\phi}{dx} = 0.$$ What I ...
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### Why don't objects bounce infinitely?

I'm computer programmer, and I was making a little test of my “possibilities”, so to speak, so I made a small game with sort of gravity, bouncing ball and walls around. Recently I've noticed that ...
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### Is there a formula showing the relationship between the number of iron cores and the output voltage of a transformer?

I know the relationship between number of turns, current and voltage of a transformer, but is there a formula showing the relationship between the number of iron cores and the output voltage of a ...
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### Work transfer to the contents of an ideal thermos flask

Assuming the thermos to be ideal and the fluid stored inside it also ideal and non-viscous. For a cold fluid, is it possible to increase the fluid's temperature by shaking the thermos flask? Can the ...
604 views

### Longest ringing/resonating object [closed]

I am interested in objects which resonate or ring for as long as possible. In particular, I am interested in Crotales (https://en.wikipedia.org/wiki/Crotales), and if it is possible to make a longer ...
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### Why is it better to accelerate electrons in a linear collider?

An accelerated charge (say an electron for simplicity) emits photons. Changing direction of movement is an acceleration. Electron-positron collisions are preferably done in linear colliders. But why ...
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### Will tsunami waves travel forever if there was no land?

If there was no land for tsunami waves to collide with, can the waves travel around the globe for forever?
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### What happens with the energy released after a particles collision?

From the website of CERN: "Collisions in the LHC generate temperatures more than 100,000 times hotter than the centre of the Sun.". My question is, what happens to the energy released after the ...
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### Where exactly does the drag force come from when using eddy currents?

I read the Wikipedia page on eddy currents and the explanation for braking confused me At the leading edge of the magnet (left side) by the right hand rule the counterclockwise current creates a ...