Re: Does gravity do work on the freely falling body?

On Apr 26, 12:59 pm, "Sue..." <suzysewns...@xxxxxxxxxxxx> wrote:
On Apr 26, 2:34 pm, Phil <acceleratedfreef...@xxxxxxxxx> wrote:


So you have the answer to your original question
by your own logic and some neat animations to
demonstrate it.

Kind regards,

Sue...

Where did you get that idea? Work over an interval can most certain be
non-zero if the speed of an object is changing (this is always
associated with change in distance wrt the center of gravity (or the
center of mass about which the object orbits).

In any even one can not conceive of gravity causing an object to
accelerate without conceiving the object responsible for its
acceleration. And so it is in the two body case the acceleration of
two bodies about a center of gravity. It is a true statement that if
one considers the accelerations of both objects that the work of one
object is equal and opposite the work of the other object. So the
work of the system is zero on a continuous basis.

Furthermore, the sum of momentum of the system is zero on a continuous
basis. And the sum of energy of the system is zero on a continuous
basis. I am well aware of this.

It is also true that a container of gas particles has a zero sum of
momentum on a continuous basis and it is further true that the sum of
energy of the particles is also zero on a continuous basis. If we put
a flame under that container, then guess what? The sum of particle
momentum and the sum of particle energy still remains zero.

Even so, the temperature rises showing that on an "individual" basis
the particles themselves are more energetic. We conceive this
increase in energy to be related to the increase in the mean speed of
the particles.

Similarly, the speeds of objects in the two body case change in
elliptical orbits and so we find the speeds of the bodies are a
maximum when they are simultaneously at perigee. So it is similar.
If adding energy to system of gas particles can cause their speed to
increase, then what about the alternate case in gravity? Where one
can ask the question how did the speed of the objects increase? It is
certainly plausible that, like the heated container of cause, energy
was added to the individual bodies (even thought the sum of that
energy, which is vector related, was zero).

This is the most useful way I know the provide an analogy. The sum of
work is vector related in both systems and it is always zero, but this
doesn't mean that the system doesn't become more energetic as
evidenced by increases in speed which are not dependent upon the of
the individual particles or objects direction of motion.
.

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