# Questions tagged [dissipation]

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### Mutual inductance and RLC circuits [closed]

I have a few general questions: Why are the different types of dampings named that way? Is there a physical reason for the solution that involves negative inside a root to be light damping? Is it due ...
215 views

### How can I express velocity as a function of position in a damped oscillation? [closed]

In a damped oscillation that obeys $x(t)=Ae^{-bt/2m}\cos(ωt)$ which shows the position of the oscillating object as a function of time, how can I express the velocity of the oscillating object as a ...
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### If at $t=0$, electromagnetic radiation was fed into the reflecting enclosure, how will the energy density within the Sphere change with time?

There is a Sphere which is $100\text{%}$ reflective by inside. And the radius of the sphere is increasing monotonically with time as $a(t)$. If at $t=0$, electromagnetic radiation was fed into the ...
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### What is the formula for how far a sound can be heard (taking into account dissipation)?

I was trying to figure out how far can a sound of 103 dB can be heard, so I converted it in W/m$^2$ (it gave me about $0.0200$ W/m$^2$) and then I used the formula “$I=P/4\pi r^2$” to find the maximum ...
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### Eternal looping water tap

If i have a container like this (filled full with water): and I unplugged the small tap, would the water pressure be big enough to blast the water to the right side of the container and cause an ...
62 views

### Heat dissipation of a Resistor

When I was studying current electricity I found out that the amount of heat dissipating across a resistor is equal to the potential energy lost by an electron. Now I thought that a resistor provides ...
59 views

### Why friction losses depend on velocity squared?

This is the reason that suction pipes of centrifugal pumps are most of the times much wider than the discharge pipes and that restriction of blood flow in arteries is always an alarming event. Does ...
25 views

### Long term solution for a driven harmonic oscillator

Let $F(t)= \cos (\omega_d t)$ be the driving force of a harmonic oscillator of mass $m$ which is damped with a damping constant $b$ such that $F= -bv$ is the damping force and the spring exerts a ...
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### Kubo formula to compute the energy dissipated in heat bath

In the case of a perturbed Hamiltonian $H_0$ \begin{equation} H=H_0 +\theta(t-t_0)W(t) \end{equation} at $t=t_0$ the Hamiltonian admits eigenvalues $E_n(t_0)$ and for positive $t-t_0$ then the ...
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### Damped harmonic oscillation (LC circuit)

The $LC$ circuit I'm considering contains a capacitor, an inductor and an electrical resistance. There is no battery: intially the capacitor has a charge $Q$ and the electric current in the circuit is ...
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### I want to know how law of conservation of energy holds in the generation of electricity in dams? [closed]

Basically law of conservation states that input energy is equal to the output energy. But i was wondering that in case of generating electricity in dams no input energy is required. As the dam only ...
37 views

### Buoyancy perpetual motion machine with compressors at top and decompress-or at bottom [closed]

a link to consideration about the perpetual motion machine [] diagrams and working out are included above. the assumptions are set to minimise engineering challenge and face perpetual motion machine ...
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### Dissipative energy intuition

Over the time i have been doing physics i have noticed a pattern related to energy that gets dissipated in systems which come to equilibrium after a certain time has passed. please hear me out with a ...
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### LC circuit with dissipation [closed]

I know that the differential equation that describes this kind of circuit is $$\frac{d^2 q(t)}{dt^2} = -\omega^2 q(t) \, .$$ I was wondering how to model the case where we have dissipation of energy. ...
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### Will a small solid body spin forever in a vacuum?

Given a small solid body like a small asteroid or satellite and some initial slow spin, for example 1 rotation every hour. If placed in a perfect vacuum with no external forces will this spin forever?...
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### Inconsistencies in Vertical Spring [duplicate]

If I attempt to find the displacement $x$, from equilibrium when a mass, $M$ is attached to an upside down vertical spring with spring constant $k$ I get two different answers when I use energy ...
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### Is the overall energy conserved in this situation?

Imagine a fully charged capacitor. This will create an electric field, and if a fixed charged particle is nearby, it will possess some amount of electric potential energy. But what happens to the ...
699 views

### Does bending your arm in space require any energy?

Since your are weightless in space, your arm has no weight, right? Does this mean that bending it in space requires no energy? Why or why not?
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### Quantum dissipation when coupling a system with a heat bath

In quantum mechanics, a good way to model dissipation of energy is to couple your system with a heat bath. This heath bath can be represented by a chain of harmonic oscillators. The Hamiltonian of the ...
4k views

### Does a fan rotating with a uniform angular velocity consume electrical energy?

Work done on a rotating body is equal to the change in its kinetic energy. When an electric fan rotates with a constant angular velocity, then its kinetic energy doesn't change. Does it mean that it ...
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### Conservation of energy, what about emitted light energy?

So, this might sound rather childish, but I was walking a dark mountain road yesterday night and started thinking a bit. My phone's battery is used to light up it's torchlight, which then is used to ...
56 views

### Physical meaning of Damped Exponential Sinusoidal [closed]

$$x(t)=A\sin(tf+p)e^{-dt}$$ The equation is used for damped exponential sinusoidal, if used for stress decomposition does it have any physical value, especially the exponential $d$?
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### Law of conservation of energy: potential energy with and without generator

Forgive my knowledgeless, Iam foreign to physics, but this one bothers me for some time now.. We have water on a high ground, thus high potential energy. Now we let the water flow down a valley. ...
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### Why does stepping on the floor produce sound?

I've been thinking about this question for some time now, and couldn't get to any conculsion. My understanding is the following: 1) when my feet and the floor are far apart (a few centimeters), they ...
710 views

### Shouldn't resistance only affect the kinetic energy of an electron?

Suppose a ball is falling from a high point and we stop it midway using a plank. Now the plank only affected the KE and total energy of the ball but not its PE. The same way, resistance is a ...
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### Do resistors heat up with left-over amps?

Apologies in advance if I misunderstand and for my bad explanation. I have heard that resistors heat up when there are left over amps that are not being used. If this is the case, why do most home ...
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### How is energy really dissipated in an electric circuit?

I've heard that in a circuit, energy is provided to separate components (lamps, motors, etc.) because of the flow of electrons. How is this possible? Since energy cannot be created, where is this ...
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### Where does energy go in joining capacitors of different capacitance charged by different potential, hypothetically assuming no resistance in circuits?

I don't understand why there is any change in initial and final energy since we have already assumed a perfectly conductive circuit. I mean, theoretically at least, there should be no change in energy....
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### Energy lost in a do-nothing machine

I recently came across this large (and very cool) do-nothing machine: do-nothing machine (video) Commentators on the internet have mentioned that the machine wastes energy, and therefore doesn't "...
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### Reversibility of equation $F=mv$ [duplicate]

Please read the following text. This text is part of Leonardo Sauskind's book. It says that the relation F = m v is reversible. Why?
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### Reversibility of the rules of classical mechanics [closed]

In the book of classical mechanics, Leonard Susskind says that Aristotle's equation of motion (F = mv) is reversible. But in the second lecture Theoretical Minimum 'videos say that F = mv is not ...
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### In a simple circuit with only cell and wire, where is the electrical energy lost (what causes potential difference)?

Imagine a simple cell circuit with a nine volts cell. Because of the cell, there is a potential difference of 9V between 2 points on the circuit. Because Energy at a point = charge * electric ...
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A bicyclist first goes up and then down a hill with constant speed. He ends up at the same height as at the start? I dont understand why to explain the law of conservation of energy my book has stated ...
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### Why does the free vibration of the spring-mass system not work in actual experiment?

Why do we not get free vibration of the spring mass system forever in reality?
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### Does friction do work or dissipate heat?

I know there are a bunch of similar questions but I read through them all and they don't answer my question. Let's say I give a box on a floor an initial "kick" of force such that it has kinetic ...
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### Cound someone help to check if this paper is talking about sound absorption coefficient of the air?

I am trying to compute the distance I stand away from a sound source and still can detect the sound although I cannot hear clearly what the speaker is saying. Given the threshold of human hearing and ...
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### How do I include friction due to normal force in Lagrange Equations?

I am going through the Goldstein book on classical mechanics and the after he derived the Lagrange equations he used Rayleigh dissipation function to include friction as a generalized force. In school ...
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### Quantising a Damped Mass on a Spring

Background: this question discusses Lagrangian/Hamiltonian formulation of a dissipative problem. However, I'm not clear if this can be made quantum and would like a more explicit roadmap if possible. ...
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### How do electrical motors obey the conservation of energy?

Feynman introduces the concept of an electromagnetic motor with this diagram. I believe I understand why the wire turns when there is current through it, because \$F = q(\mathbf{E} + \mathbf{v} \times ...
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### Calculating the total time elapsed until two pendulums “stop colliding” gives a divergent result [closed]

Setup Consider the following situation: Two (small) balls hang by two identical ideal threads, such that in their initial states the threads are perfectly vertical. The two balls are moved by small, ...
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### Why must all natural processes be irreversible?

My thermodynamics lecturer was talking about reversibility and the idea of spontaneous change and he mentioned that all natural processes are irreversible. Can someone offer some sort of proof or ...