I think the rules imply it is true for both linear and angular momentum. No amount of the total momentum of a system can be converted into heat. However, some amount of the total energy of a system can be converted into heat. Is it possible to convert all of the energy into heat?
Harry On Mon, Feb 10, 2014 at 10:59 PM, David Roberson <dlrober...@aol.com> wrote: > I do not see where we differ in understanding Bob. The system you > describe had nearly zero total angular momentum before and after the > collision so it remains conserved. The rotational energy can be extracted > by various means as I also stated. > > Harry has concluded that angular momentum can not be converted into heat, > which is always true. He also states that angular energy can be converted > into other forms or energy including heat. Can you demonstrate a closed > system where this is not the case? > > Dave > > > > -----Original Message----- > From: Bob Cook <frobertc...@hotmail.com> > To: vortex-l <vortex-l@eskimo.com> > Sent: Mon, Feb 10, 2014 10:46 pm > Subject: Re: [Vo]:Energy and momentum / was RAR > > Harry and Dave--Bob Cook here-- > > Keep in mind that the law is that angular momentum must be conserved. > However systems with angular momentum can also have significant energy that > can be changed to heat. > > Take two planets in the solar system with direction of rotation in > opposite directions. One planet with a vector pointing to the North Star > and other one with its vector pointing in a direction opposite to the North > Star. They drift slowly together and eventually collide. If they have > about equal mass and size and collide their total angular will approach > zero. However there will be a lot of heat energy released. Angular > momentum is a vector quantity--energy is a scalar with no direction > attached. This holds for quantum systems with the Spin quantum angular > momentum J associated with particles being a vector quantity. Electrons > pair up to reduce their angular momentum to zero. Many quantum systems of > particles tend to low spin states since low is consistent with the lowest > energy state, and consistent with reactions that increase their > entropy--the second law of thermodynamics. > > I think you two are forgetting the vector nature of angular momentum > and mechanisms for its conservation. > > I do not agree with Harry's corollary. > > Bob > > ----- Original Message ----- > *From:* David Roberson <dlrober...@aol.com> > *To:* vortex-l@eskimo.com > *Sent:* Monday, February 10, 2014 6:19 PM > *Subject:* Re: [Vo]:Energy and momentum / was RAR > > Your corollary would be an excellent addition to my discussion. > > Dave > > > > -----Original Message----- > From: H Veeder <hveeder...@gmail.com> > To: vortex-l <vortex-l@eskimo.com> > Sent: Mon, Feb 10, 2014 5:49 pm > Subject: Re: [Vo]:Energy and momentum / was RAR > > > > > > > > On Sun, Feb 9, 2014 at 7:17 PM, David Roberson <dlrober...@aol.com> wrote: > >> OK. Energy is proportional to velocity squared. If you double the >> velocity, you have four times as much energy as in the first case. Also >> the direction of the motion is not important. For example, a ball moving >> to the right has a certain amount of energy and a second one moving to the >> left with the same mass and velocity will have the same amount as well. >> Energy adds, so you have two times the amount contained within one. >> >> Momentum is proportional to velocity directly. The direction of the >> movement is important since momentum is a vector quantity, unlike energy. >> The two ball case above results in a net momentum for the system of zero. >> The two vectors are equal and point in opposite directions so they cancel. >> >> Energy and momentum require different rules of behavior and can not be >> interchanged. >> >> Dave > > > That is a good summary. > As a corollary to the last statement, I would add that momentum cannot be > turned into heat since heat is considered a form of energy. > > Harry > >
