Questions tagged [dissipation]

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1answer
22 views

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 ...
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1answer
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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0answers
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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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1answer
56 views

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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1answer
26 views

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 ...
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2answers
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 ...
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1answer
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 ...
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1answer
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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1answer
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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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2answers
31 views

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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3answers
52 views

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 ...
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1answer
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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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1answer
50 views

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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2answers
50 views

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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1answer
56 views

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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1answer
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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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2answers
37 views

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 ...
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6answers
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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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0answers
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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 ...
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7answers
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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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2answers
41 views

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 ...
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1answer
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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1answer
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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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1answer
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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 ...
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4answers
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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3answers
70 views

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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3answers
67 views

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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4answers
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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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2answers
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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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0answers
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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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1answer
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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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1answer
40 views

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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1answer
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Confusion about energy changes

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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2answers
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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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1answer
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Why does the angular frequency ω changes during the damping oscillations?

I can understand why $ω$ in the damped system is smaller than the intrinsic $ω_0$, but why does he say 'angular frequency $ω$ changes during the damping oscillations'? The equation between $ω$ and $...
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1answer
55 views

What are the factors that affect the dampening of spring-mass system? [closed]

I'm trying to investigate how different values of spring constant affect the changes in amplitude and period of oscillations while the spring-mass system undergoes dampening. However, I have to make ...
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2answers
83 views

Why do waves disappear after some time?

When a stone is thrown in water then transverse waves are formed. But they get slow and disappear after sometime. Why? Similarly it happens in longitudinal waves. When we speak, after sometime our ...
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0answers
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Statistical definitions of heat and work

My understanding of heat and work from a statistical mechanics perspective (mainly extracted from Schrödinger's Statistical Thermodynamics) is as follows. We have some system, let us say a box of gas....
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2answers
159 views

A proof that air resistance isn't conservative

I want to show that a force depending on the velocity $\dot{\underline{r}}$, where $\underline{r}$ is the position vector of a particle, cannot be conservative since there is energy dissipation. Here, ...
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3answers
144 views

Why does the reversible adiabatic expansion do more work on the surroundings compared to the irreversible adiabatic expansion?

I am wondering why a reversible adiabatic expansion results in a higher work output on the surroundings though the irreversible adiabatic expansion has to overcome the frictional force and therefore, ...
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3answers
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How do we dampen a spring-mass system with respect to time?

Here https://en.wikipedia.org/wiki/Harmonic_oscillator we have an equation for displacement of a mass on a string as a function of time. ${\displaystyle x(t)=A\cos \left({\sqrt {\frac {k}{m}}}t\right)...
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4answers
109 views

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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1answer
25 views

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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4answers
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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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1answer
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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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1answer
84 views

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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2answers
512 views

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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2answers
162 views

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 ...
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1answer
61 views

How the total energy of a LC oscillator remains unchanged while placing a coil near the inductor of the LC oscillator?

If the capacitor is initially charged with Q charge and then conected to a inuctor then discharging takes place and the energy stored in electric field gets converted into the energy stored in ...
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0answers
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Where are the hysteresis losses?

I have some troubles to understand what are the hysteresis losses on a magnetic hysteresis loop of a ferromagnetic material. First question, is there a law which say that the product of the magnetic ...

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