Definition of "Gravity is conservative" ?

[nicbordeaux]

Input particularly appreciated from Wubbly, Fletcher and Ovyyus for purely financial reasons... but all input most welcome.

Please define clearly what is meant by "Gravity is conservative". Thx

Nick

[Unbalanced]

Nicbordeaux; I have no financial motive but I hope I can convey to you what is meant by the term "conservative force" as it applies to physical laws of nature.


The force exerted by gravity on a mass moving in an upward direction is equal to the force exerted by gravity on the same mass moving in a downward direction.

A conservative force transfers energy "to" and "from" an object during a closed path motion in equal measure.

In other words, the total work done by a conservative force in a closed path motion is exactly zero.

In physics a force is said to be conservative when it maintains a constant overall total. It is not expended (used up)

In a closed loop system such as a classic wheel, it is as though gravity does not exist. It is not a useable force. Whatever may be gained from it on the one side of the axis will necessarily be subtracted from it in equal measure on the opposite side of the axis.

As discouraging as this definition may seem to the would-be gravity wheel designer, it should kept in mind that anomalies (exceptions to accepted laws of nature) do exist and though exceedingly improbable, it should not necessarily be classed as impossible, that some configuration of weight and levers etc. may allow for an exception to this definition of gravity as a conservative force, i.e. when pigs fly.

[Unbalanced]

Accidental DP see Below

[Unbalanced]

Examples of Natural Anomalies (Observed Exceptions to Accepted Laws of Physics)

Gravitational Anomalies
http://en.wikipedia.org/wiki/Gravitation

Tunguska event
http://en.wikipedia.org/wiki/Tunguska_Explosion

Other Naturally Occurring Anomalies
http://en.wikipedia.org/wiki/Anomalies

[ovyyus]

Gravity acts like the perfect lossless spring. Just like a spring, it can only give back what is first put in.

[Unbalanced]

A spring is a perfect example given the qualifier:

less the losses caused by non-conservative forces such as friction and wind resistance etc.

Time to get back to my other lives

[rlortie]

Curtis wrote;

The force exerted by gravity on a mass moving in an upward direction is equal to the force exerted by gravity on the same mass moving in a downward direction.

Sorry partner but I question this statement. If the upward force is equal then you are at a standstill not unlike the magnet on the refrigerator. To raise upward you must not only equal the force of gravity but surpass it to achieve movement better known as 'WORK'

I fear that with this thought in mind it is going to blow a lot of holes in various designs by numerous members.

To test this; balance a teeter totter to dead center or COM, it will not seek horizontal but will stop/rest at any angle you set it at.

Equal forces being equal, there is no gradient differential therefore no work can be accomplished.

Ralph

[nicbordeaux]

On PM forums, conservative nature of gravity seem's to be understood as :

1) a OB wheel won't do a full turn with a 12 OB release because gravity is conservative, therfore you need power from somewhere or some arrangement to get a full turn. The less than full turn is often named underunity, a full turn would be overunity.

2) no device can under the initial pull of G on a OB raise vertically the sum total of it's component mass to a greater height than that at which it started from.

Anything else fit the bill as a acceptable definition of "gravity is conservative" in the great wild west of Overunity ?

[jim_mich]

Nic, that pretty much sums up the meaning of gravity being conservative.

[FunWithGravity2]

On PM forums, conservative nature of gravity seem's to be understood as :

1) a OB wheel won't do a full turn with a 12 OB release because gravity is conservative, therfore you need power from somewhere or some arrangement to get a full turn. The less than full turn is often named underunity, a full turn would be overunity.With all parts of mechanism able to repeat process and no one part removed or at a lower total COG

2) no device can under the initial pull of G on a OB raise vertically the sum total of it's component mass to a greater height than that at which it started from.

Anything else fit the bill as a acceptable definition of "gravity is conservative" in the great wild west of Overunity ?

I believe those with money at stake may want to explain preload to nick before the "proof" of his overunity is presented. Just to save needless pages of arguing about the "proof"


JMHO

[greendoor]

Conservation applies to things which are in short supply and need to be conserved.

People compare gravity to a spring, and claim that you can only get out of it what you put into it. This is a very closed mind view, which I hope I can demolish with the following ...

Slingshot effect. http://en.wikipedia.org/wiki/Gravity_assist

Space craft can use the free energy of gravitational attraction to greatly reduce their fuel requirement.

This proves that gravity can be used as an energy source - a fuel if you will. The space craft are benefiting from "getting out" energy which they did not have to "put in".

Period.

Those totally committed to being a know-it-all skeptic will try to argue that this is simply removing energy from the planet, and the planet rotation will slow down slightly - or whatever theory helps to quell the panic arising in their chest. All utter bollocks, probably. This presupposes that we know exactly what gravity is and what causes it. Which we don't.

We don't need to know how gravity works to make earth-based machines - just that there is a downwards force vector acting on all mass.

To those who argue that gravity acts like a spring, and say "we can only get out what we put in" - I would say that is only one way in which we can use it. The slingshot effect is another way, where obviously we can get out much more than what we put in. And I believe there are earth-based ways of extracting free energy from gravity.

Think about a river with a steady flow of water. Insert a bucket on a rope into this stream. We experience a Force vector acting on the rope. Can we use this Force to perform useful Work? Yes - but as the bucket gets pulled downstream, we end up having to reel the bucket back in again. To do this, we have to apply an equal and opposite Force for the same amount of Time. So do we give up and say that a flowing river is Conservative - we can only get out what we put in?

Well if we insist on doing it this way - yes, we can't can't get out any more than what we put in. It is acting like a spring.

With the benefit of hindsight, we all know that we can make a waterwheel and extract real useful work from a flowing river. But imagine if we had never invented the water wheel, and still didn't know how to get power out of flowing water ...

With a water wheel (or wind mill) we have to cycle our machine to get energy from the water flowing downstream, but then return the working part of our machine upstream but somehow using less energy than what we obtained going downstream. This makes the process less efficient, because the available power is the difference between the gain and the loss. But since the flowing stream is free and continuously available, we don't care.

So maybe - just maybe - gravity is like that flowing stream. Yes - we can choose to use it like a spring, and only take what we put into it. But maybe we find a way to return a mass with less energy than what we can obtain out of it's fall.

Science has a history of armchair experts proclaiming the impossibility of certain things. It doesn't stop some people from just going ahead and building stuff that works.

[rlortie]

greendoor,

Think about a river with a steady flow of water. Insert a bucket on a rope into this stream. We experience a Force vector acting on the rope. Can we use this Force to perform useful Work? Yes - but as the bucket gets pulled downstream, we end up having to reel the bucket back in again. To do this, we have to apply an equal and opposite Force for the same amount of Time. So do we give up and say that a flowing river is Conservative - we can only get out what we put in?

As I pointed on on another thread, we have all gone along with the notion that an equal and opposite force (I will leave time out of this) must be applied to return the bucket upstream.

This is my problem; An equal applied force will only stop the bucket from traveling downstream, that is to say you have equaled and or canceled. It will take more force to return it upstream. This of course also holds true to my thinking of gravity.

Would you care to give your opinion on this, I would really like to hear some input.

Ralph

[ovyyus]

Space craft can use the free energy of gravitational attraction to greatly reduce their fuel requirement.

This proves that gravity can be used as an energy source - a fuel if you will. The space craft are benefiting from "getting out" energy which they did not have to "put in".

Period.

Someone doesn't understand the 'gravity assist' maneuver. Spacecraft momentum gain is at the expense of planet momentum loss. Small belief + big agenda = woolly thinking.

Science has a history of armchair experts proclaiming...

Beautifully ironic :D

[nicbordeaux]

greendoor,

Think about a river with a steady flow of water. Insert a bucket on a rope into this stream. We experience a Force vector acting on the rope. Can we use this Force to perform useful Work? Yes - but as the bucket gets pulled downstream, we end up having to reel the bucket back in again. To do this, we have to apply an equal and opposite Force for the same amount of Time. So do we give up and say that a flowing river is Conservative - we can only get out what we put in?

As I pointed on on another thread, we have all gone along with the notion that an equal and opposite force (I will leave time out of this) must be applied to return the bucket upstream.

This is my problem; An equal applied force will only stop the bucket from traveling downstream, that is to say you have equaled and or canceled. It will take more force to return it upstream. This of course also holds true to my thinking of gravity.

Would you care to give your opinion on this, I would really like to hear some input.

Ralph

Equal forces or more force required to move upstream in the flowing water analogy, there is the other case : lateral thinking. If you design your bucket so that at the end of "x" distance travelled via the force of water flow it rises to the surface and you can reverse it so it empties under gravity, you can then with a nicely designed bucket apply a bit of rewind force on it's rope to skip it over the surface. The net result is a positive for you. No physics laws blown apart, just good mechanical trick.

[ruggerodk]

...We don't need to know how gravity works to make earth-based machines - just that there is a downwards force vector acting on all mass.
...So maybe - just maybe - gravity is like that flowing stream. Yes - we can choose to use it like a spring, and only take what we put into it. But maybe we find a way to return a mass with less energy than what we can obtain out of it's fall.

Or maybe not.
A flowing stream is - unequal to gravity - of mass and is constituted by displacement of this mass within some kind of time reference.
While displacement is all about time, time is not allways the right time.
At first sight a mass resting on the ground has no time reference but is still under the influence of gravity.
So maybe it's not a question of harnessing gravity - but of time instead.

regards
ruggero ;-)