All Questions
Tagged with conservation-laws energy-conservation
257
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Does moving the idler in a wheel and disk CVT conserve energy or momentum? [closed]
Consider the wheel and disk CVTs (continuous variable transmissions) below. Configuration A comprises a CVT disk coupled to the "system under control" 's', whereby a control wheel 'cw' ...
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How can a free electron and an ion in a plasma recombine without violating conservation of energy and momentum?
This question is the inverse of How does ionization of gas molecule affect the translational kinetic energy of the molecule?
The answer to that question is that a molecule cannot spontaneously ionize: ...
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Energy and momentum conservation for light reflection [duplicate]
There is a radiation pressure which means that when light reflects from a surface, the surface will get some momentum/energy.
If so, what is the balancing change on the light/radiation side if light ...
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Why exactly does time translation symmetry lead to conservation of energy? [duplicate]
As far as I know (and I don't know much), Noether's theorem claims that time translation invariance of the laws of physics leads to the conservation of energy. The way I understand it is that if we ...
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Energy created by gravity
So just a thought experiment: I take my rocket and fly through space. Meanwhile I pick up some piece of debris that experiences no (big) gravitational pull. I attach it with an infinitely long rope to ...
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3
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Rolling in opposite direction to linear motion
In this blog about a cylinder rolling up a frictionless incline, the author concludes that the cylinder will still be spinning clockwise at the top of its ascent up the hill and will then descend with ...
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Equations of motion for a force in special relativity seem to require a differential equation — in this context, what does Kinetic Energy *mean*?
I was faced with a situation where I suddenly realized that although Kinetic Energy in Special Relativity is defined as
$KE=\gamma m_0 c^2 - m_0 c^2$
The work energy theorem says
$\Delta KE +\Delta ...
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Where did potential energy disappear in this case?
Just a new thought experiment. We know that the kinetic energy depends on frame of reference as do work and velocity. Now we can consider a falling ball. It converts potential energy to kinetic energy ...
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Do we know that energy of a system is conserved if no external forces do work on it?
This question is from K&K's intro book on mechanics. The larger block with the quarter circle missing has mass $M$ and the smaller block has mass $m$. The goal is to find the speed $v$ of the ...
2
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1
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Is conservation of energy a local law in Quantum field theory? [closed]
From Wikipedia,
"The local energy conservation in quantum field theory is ensured by the quantum Noether's theorem for the energy-momentum tensor operator. Thus energy is conserved by the normal ...
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Why does my perpetual CMBR rocket ship not work? Why does the CMBR have infinite energy?
Take a spaceship and accelerate it to 99.947% the speed of light, effectively blueshifting the Cosmic Microwave Background (CMB) from 1.9mm to 500nm, turning the CMB to a harvestable source of energy. ...
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Three masses connected by a string (momentum conservation) [closed]
Three identical balls each of mass m = 0.5 kg are connected with each other as shown in figure and rest over a smooth horizontal table. At moment t=0, ball B is imparted a horizontal velocity v=9m/s. ...
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How can conservation of momentum coexist with conservation of energy? [closed]
COM posits that Mass*Velocity is constant, and COE posits that 0.5*mass*velocity^2 is constant.
If i have a 10kg box moving left at 10m/s, it has Momentum of 100 and Kinetic energy of 500.
If i then ...
6
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Why are the Navier-Stokes equations inconsistent in this case?
Consider the case of a one-dimensional incompressible, non-viscous fluid flowing down a vertical pipe under the influence of gravity. Since we assume the flow is constant along the cross section of ...
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Basics of Nuclear reaction
In the nuclear physics book by Krane, I was reading about how mathematically and numerically Q value of the reaction are measured. So he decided to prove it by solving it in Lab frame, And he goes ...
