# Questions tagged [dissipation]

The tag has no usage guidance.

37 questions
Filter by
Sorted by
Tagged with
3k views

### Why can't we ascribe a (possibly velocity dependent) potential to a dissipative force?

Sorry if this is a silly question but I cant get my head around it.
4k views

### Lagrangian and Hamiltonian EOM with dissipative force

I am trying to write the Lagrangian and Hamiltonian for the forced Harmonic oscillator before quantizing it to get to the quantum picture. For EOM $$m\ddot{q}+\beta\dot{q}+kq=f(t),$$ I write the ...
3k views

### How do non-conservative forces affect Lagrange equations?

If we have a system and we know all the degrees of freedom, we can find the Lagrangian of the dynamical system. What happens if we apply some non-conservative forces in the system? I mean how to deal ...
3k views

819 views

### Is a superconductor really a super conductor?

It is known that a superconductor is a material with electrical resistance zero. My question is, it is exactly zero, a theoretical zero, or for practical realistic reasons it is effectively zero?
432 views

### RLC circuit - calculating resonant frequency

If I take a series RLC circuit connected to a battery, the impedance is minimized when $\omega = \frac{1}{\sqrt{LC}}$. I also know that the series RLC circuit is analogous to a damped driven harmonic ...
551 views

### Friction during pure rotation

I have already read Role of friction during pure rolling What is the direction of the friction force on a rolling ball? Rolling resistance and static friction and many others But I still have the ...
504 views

### Friction in Lagrangian formulation

We know the Lagrange equations are: $$\frac{\partial \mathcal{L}}{\partial q_i}-\frac{d}{dt}\left(\frac{\partial \mathcal{L}}{\partial \dot{q_i}}\right)=0.$$ Then, when we add friction in there, we ...
1k views

### What are the reasons for leaving the dissipative energy term out of the Hamiltonian when writing the Lyapunov function?

I have a problem with one of my study questions for an oral exam: The Hamiltonian of a nonlinear mechanical system, i.e. the sum of the kinetic and potential energies, is often used as a Lyapunov ...
5k views

### Liouville's theorem and conservation of phase space volume

It can be proved that the size of an initial volume element in phase space remain constant in time even for time-dependent Hamiltonians. So I was wondering whether it is still true even when the ...
25k views

### Why does friction produce heat?

What causes two objects sliding against each other to produce heat? Why don't they generate visible light or something else?
545 views

### What physical processes may underly the collisional term in the Boltzmann equation, and how do they increase entropy?

Consider particles interacting only by long-range (inverse square law) forces, either attractive or repulsive. I am comfortable with the idea that their behavior may be described by the collsionless ...
641 views

### Saving energy while charging capacitor

While charging a capacitor by a DC source, half energy is wasted as heat. Can't we save that energy? Here I am talking about $$(1/2)CV^2$$ which is wasted while supplying $$CV^2$$
396 views

### Why current loses its energy?

Can someone explain or give a link to explanation why current loses its energy? For example in simple circuit with lamp. I understand that the energy is spent for heating and lighting. But how exactly ...
136 views

### Are gravitational waves dissipated and what is the mechanism? [duplicate]

I was amazed by the fact that we have been able to detect gravitational waves created thousands of year before they were observed. My surprise is that any wave phenomena I know it is always dissipated,...
108 views

109 views

### Why do energy transfers always result some heat loss?

explain that energy transfers and transformations in mechanical systems always result in some heat loss to the environment. Like why is it necessary for a heat loss?
126 views

### Why can't friction in an accretion disk radiate away enough of the angular momentum do create inward spiral?

As almost every source that I'd found explains, it was a challenge for scientists to understand the mechanism by which the total angular momentum in the accretion disc was conserved, while taking the ...
270 views

### Orbit in the vacuum

As the space is a vacuum and there is no friction in space, Can we assume that, if we place an object in gravity in exactly the right distance from a planet with gravity and in the right acceleration, ...
661 views

### Dissipation and first law of thermodynamics

Consider the following situation: a certain gas is contained in a well-insulated cylinder with a well-insulated piston head. Now, in this case the piston is not frictionless. In order for the piston ...
50 views

### Can a Peltier/Seebeck cell transfer energy from a “thermally insulated” system converting (a part of) thermal energy into electrical energy?

Suppose you have a closed system, as per the schema attached below, which walls are thermally insulated. Suppose you want to reduce the temperature of the fluid inside the closed system, without ...
1k views

### What slows down a fidget spinner more: air resistance, or friction from the bearing?

So "fidget spinners" are now massively popular. I got one, and it occurred to me that I'm not sure which force is more important in slowing them: friction in the bearing, or air resistance acting on ...
198 views

### Energy doesn't get lost? Basic understanding, please [duplicate]

If its true that energy isn't lost, its just transferred, where did the energy go from a falling object that hits the floor and stays there? It started with the most gravitational potential energy, a ...
80 views

### Help with my bouncy ball lab (I know the factors just not how to approach them) [closed]

In my physics lab we need to determine the factors that account for the energy "loss" during a high bounce ball bounce. I know that energy is "lost" (not really) to heat, air resistance, and sound. ...
494 views

### Why not use our own light production to produce new energy instead of wasting it?

Why don't we use our own light production at night (I mean home, buildings, streets,..., lighting) to charge photovoltaic panels instead of wasting it?
The forced oscillation with damping is described as $$\frac{d^2x}{dt^2}+\gamma\frac{dx}{dt}+\omega_0^2x=\frac{F_0}{m}\cos{\omega t}$$ Its solution is $x=A\cos{(\omega t-\delta)}$, with A(\omega)=...