# Questions tagged [conservation-laws]

The statement that a property of a system does not change if the system is isolated.

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### Does gravity actually have a ‘reaction force’? [duplicate]

By (my limited knowledge of) Einstein’s theory of General Relativity, as gravity is not a force but rather the effect of an object’s inertial path following a geodesic through curved spacetime due to ...
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### How to check conservation laws of particles the quantities are not valid for? [closed]

The question is for all cases where quantities such as strangeness and isospin can't be checked For example e+ + e- -> photon + photon In this reaction, we can't check for isospin or its component, ...
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### Is there momentum conservation in photoelectric emission? [closed]

There is actually a question in my textbook which I am unable to understand.I didn't understand anything
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### Doubt Regarding Noether's theorem for time-dependent systems

I'm having problems showing Noether's theorem when the lagrangian is time dependent. I'm trying to do it not using infinitesimal transformations from the beginning, but continuous transformations of a ...
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### Pendulum attached to a cart: is momentum conserved?

Both the cart and the pendulum have velocity=0 at time=0, pendulum is held at that angle θ and then released.Frictions are negligible. Is there an axis along which linear momentum is conserved? I've ...
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### Using Galilean transformation to solve a question with a block-spring-block system [closed]

I am currently practicing for my PHYS 101 major test and encountered this question: In Figure 11, block 1 (mass 2.50 kg) is moving rightward at 10.0 m/s and block 2 (mass 6.20 kg) is moving rightward ...
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### How is the momentum conserved in the case of recombination in direct bandgap semiconductor?

In the case of a direct bandgap semiconductor, the recombination of an electron and a hole generates a photon that has energy equal to the bandgap of the semiconductor, accounting for energy ...
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### What is the intuitive reason why Ampere's law is incorrect?

I don't understand why Ampere's Law for magnetic fields is wrong. So initially, we got taught it as the following: $$\vec\nabla\times\vec{B}=\mu_0\vec{J}$$ and this turns out to be wrong. I also ...
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