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
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
