Questions tagged [dissipation]
552 questions
93
votes
9 answers
When I walk down the stairs where does my potential energy go?
When I leave my room I walk down three flights of stairs releasing about $7\,\text{kJ}$ of potential energy. Where does it go? Is it all getting dispersed into heat and sound? Is that heat being generated at the point of impact between my feet and…
A. Kriegman
- 1,303
74
votes
5 answers
Why does a system try to minimize its total energy?
Why does a system like to minimize its total energy? For example, the total energy of a $H_2$ molecule is smaller than the that of two two isolated hydrogen atoms and that is why two $H$ atoms try to form a covalent bond. According to the classical…
SRS
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56
votes
3 answers
Why doesn't this perpetual motion machine using the buoyant force work?
I realize this isn't possible, but I can't see why not, especially if you change the model a little bit so that the balls simply travel through a tube of water on the way up, rather than exactly this model.
Please be clear and detailed. I've heard…
Martin
- 579
41
votes
5 answers
Can you bend light to go in a circle?
Is it possible to bend light so that it forms a circle and goes round and round indefinitely without losing energy?
macco
- 2,015
35
votes
3 answers
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 Lagrangian
$$…
user56199
34
votes
13 answers
How is it possible to know a proposed perpetual motion machine won't work without even looking at it?
It is often said that perpetual motion is impossible. Many people try to invent perpetual motion machines. Apparently every such attempt is doomed to failure. People don't even need to look at one to know this. What is it about perpetual motion that…
mmesser314
- 49,702
26
votes
4 answers
Why can't we ascribe a (possibly velocity dependent) potential to a dissipative force?
Sorry if this is a silly question but I cant get my head around it.
yayu
- 4,982
24
votes
10 answers
What happens to half of the energy in a circuit with a capacitor?
For a simple circuit with a battery supplying a voltage $V$ to a capacitor, let us assume that the charge on the capacitor is $Q$. Now, the work done by the battery or the energy supplied is given by the relation:
$$W=QV$$
But the energy stored in…
Tabish Mir
- 457
21
votes
7 answers
Storage of Light
Hypothetically speaking, if one had a hollow sphere that had a perfectly polished mirrored interior surface with little to no light absorption, and then sought to fill the interior space by introducing light via a very small opening (perhaps using…
18
votes
3 answers
Can we quantize Aristotelian physics?
Aristotelian physics, shorn of whatever the historical Aristotle actually believed, is pretty similar to Newtonian physics. Instead of "An object in motion stays in motion unless acted on by an unbalanced force", we have "An object at rest stays at…
Keshav Srinivasan
- 3,139
18
votes
3 answers
Rocket attached to a pendulum. How is energy conserved?
I'm trying to wrap my head around a conceptual problem involving a simple pendulum with a rocket attached to its mass. Imagine the rocket expels gas to provide a tangential thrust force. However, the thrust is calibrated such that it's not…
Eduardo González
- 183
18
votes
5 answers
Is there a fundamental reason for the exponential dependence of the evolution of the temperature in an electronic deviced that is powered on?
I used an electronic device during a certain time. Due to the powering of this device, the temperature, measured with an NTC, increased. After a certain time, I switched off the power of the device but still measured the temperature, with the…
18
votes
4 answers
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?
Bodvarion
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18
votes
1 answer
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 with the Lagrangian, if we get any external…
user58143
17
votes
4 answers
What exactly makes a force conservative?
I get that forces can be classified as either conservative or non-conservative, depending on whether the work done in a round trip is zero or non-zero.
What property of the force makes it to be, conservative or non-conservative, so that the work…
vs_292
- 957