Naked Science Forum

Non Life Sciences => Physics, Astronomy & Cosmology => Topic started by: jeffreyH on 19/12/2017 12:46:54

Title: Can kinetic energy be distributed?
Post by: jeffreyH on 19/12/2017 12:46:54
If three identical particles collide with the same kinetic energy is there a way for this collision to produce different resulting kinetic energies after the collision. They don't have to all collide simultaneously.
Title: Re: Can kinetic energy be distributed?
Post by: Colin2B on 19/12/2017 13:04:59
If the particles are idealised billiard balls, yes, because you can set up differing angles of approach. Also different timing for collision will do same.
However, KEin=KEout.

PS But you know that already, so there must be a deeper question behind this one.
Title: Re: Can kinetic energy be distributed?
Post by: chiralSPO on 19/12/2017 14:23:44
Ein = Eout but it doesn't have to remain as kinetic energy. For example:

• Imagine the three particles (each having mass) are in a gravitational field--the collision could result in one (or more) of the particles moving to a higher potential energy within the field, at the expense of the combined kinetic energy of the system (converting kinetic energy into potential energy).

• Or, we could imagine that the particles have internal structure, and that a collision could change one (or more) of the particles to an excited state (for atoms, this could be a change in electronic state, for molecules it could be a change in vibrational and/or electronic state, or there could be some other kind of internal strain caused by the collision) (again, converting kinetic energy into potential energy, or into internal kinetic energy, in the case of vibration)
Title: Re: Can kinetic energy be distributed?
Post by: jeffreyH on 19/12/2017 19:19:19
If the particles are idealised billiard balls, yes, because you can set up differing angles of approach. Also different timing for collision will do same.
However, KEin=KEout.

PS But you know that already, so there must be a deeper question behind this one.

Yes.
Title: Re: Can kinetic energy be distributed?
Post by: evan_au on 19/12/2017 21:26:43
I would say that as soon as you reach three or more interacting objects, you are starting to enter the domain of thermodynamics, where the results of the interaction will take on a distribution of energies.

We normally apply the statistics of thermodynamics to very large systems (1020 or more interacting particles), but it can be glimpsed in much smaller systems too.
Title: Re: Can kinetic energy be distributed?
Post by: jeffreyH on 19/12/2017 22:26:48
I am heading towards quantum thermodynamics. Although it looks quite mean.
https://en.m.wikipedia.org/wiki/Quantum_thermodynamics
Title: Re: Can kinetic energy be distributed?
Post by: jeffreyH on 19/12/2017 22:44:00
I am also looking at this.
http://m.sparknotes.com/physics/workenergypower/workpower/section2.rhtml
Title: Re: Can kinetic energy be distributed?
Post by: jeffreyH on 20/12/2017 17:56:56
So if we have an idealised system with a number of particles all with the same kinetic energy can any useful work be done by the system? Think of the system as in total isolation and any number of particles. Basically starting from a state of equilibrium.
Title: Re: Can kinetic energy be distributed?
Post by: jeffreyH on 20/12/2017 18:20:43
Please bear this in mind.
https://en.m.wikipedia.org/wiki/Open_quantum_system
Title: Re: Can kinetic energy be distributed?
Post by: yor_on on 22/12/2017 09:24:41

http://www.physicscentral.com/explore/action/negative-temperature.cfm
Title: Re: Can kinetic energy be distributed?
Post by: jeffreyH on 22/12/2017 09:57:21
Excellent find yor_on!