[time-nuts] FW: Pendulums & Atomic Clocks & Gravity

Arnold Tibus Arnold.Tibus at gmx.de
Mon May 28 17:41:18 EDT 2007


Ulrich, 
I think I am with you, but
let me see wether my simple understanding is correct: 

Assuming a object without sensitivity to gravity flying with a 
certain (high) speed across space approaching planet terra. 
The path of this object would be obviously straight as a line 
(as long we are not thinking in astronomical dimensions) , and even 
passing the planet in a very short distance, nothing would deviate 
this object from this straight way. 
If suddenly, only for a short moment, the bypassing object would get 
mass, the gravity of both bodys would play its role and accelerate 
this mass into direction of the planet, and vice versa. Due to the 
immens big mass difference we forget here the orbit or path change 
of the planet. The accelerated object does change the direction 
somewhat into the planets center of gravity. The amount depends 
on the relation between the impulse with direction and the gravitational 
impact at that momentary position. After a bend in the path and a 
switch off of the object's gravity, the passing object would 
continue the straight flight but in a new direction.
As in reality there is no possibilty for such tricks, the approaching object 
will receive continuously these deviating gravity impacts, therefore
beeing continuously accelerated to deviate from the linear path 
into a orbitical path, if the gravity force is of the right amount, if not 
this body will end with an impact or escape after a longer curvature. 
Again back on (a new) straight path out of the gravity from 
celestial bodys, there are no more other forces acting on this object. 
This free flying object does not need any further force or energy to 
contiue its way until other forces will stop the way. 
Where this object finally did come from, does not change the facts, 
this object could have been launched from the planet terra as well, 
accelerated sufficiently to end as satellite or as spacevehicle on the 
way out of the solar system. 
Thinking this way, I could not find any centrifugal forces, active 
was only the gravity between this bodys fighting with impuls of the 
object. Would this body not just fall down vertically without own 
impuls or impetus? 
I think the problem thinking on centrifuges is, that the surroundig 
object is getting not only the fixation to avoid to escape but as well 
the tangential speed / impuls via the coupling and the continuous 
acceleration forcing into a circular path. 
The outcome should be the same as above.

Just a short analogon for auquatic fans: Driving a ship straight ahaid 
with the rudder straight in the middle, the course will be like a line. 
Then switching the jet-rudder in the bow on, the water-jet will deviate to 
a circular course with the same effects, we do sense the acceleration....

73

Arnold, DK2WT




On Mon, 28 May 2007 21:15:08 +0200, Ulrich Bangert wrote:

>Didier, 

>> Since you know a lot more about this than I do, I will accept 
>> your statement that centrifugal forces (or more generally 
>> inertial forces) are fictitious, but only because you insist. 
>> As long as I can predict their effect and calculate their 
>> magnitude, that's all this engineer is interested in :-)

>That would be totally wrong! You are just missing the possibility to
>gain some new insights into nature.

>> Your comparison with the linear motion is not valid.

>Please note that my intention was not to immediatly compare linear to
>circle motion. The example was merely to show you something about about
>forces and counterforces. You did not excactly understand it so let me
>try to take a second chance:

>> Inertia causes real forces to be developed.

>If this sentence is true then please answer again the following
>question: Is there a real inertial counterforce in the linear example or
>not? 

>73s and my best regards
>Ulrich, DF6JB

>> -----Ursprüngliche Nachricht-----
>> Von: time-nuts-bounces at febo.com 
>> [mailto:time-nuts-bounces at febo.com] Im Auftrag von Didier Juges
>> Gesendet: Montag, 28. Mai 2007 17:59
>> An: 'Discussion of precise time and frequency measurement'
>> Betreff: Re: [time-nuts] FW: Pendulums & Atomic Clocks & Gravity
>> 
>> 
>> Ulrich,
>> 
>> Your comparison with the linear motion is not valid. While 
>> you push the body, it accelerates. The energy spent giving 
>> the body increased speed (due to the excess force applied to 
>> the body while there is no counter
>> force) is stored in kinetic energy. Once you stop pushing, 
>> the body moves straight at constant speed and there is no 
>> more force either way, the state of motion does not change.
>> 
>> Going back to the satellite, I believe we agree in principal 
>> but you are hung up on the first law definition. The 
>> corollary to the first law is that objects resist change to 
>> their state of motion. They resist that change via inertia. 
>> Inertia causes real forces to be developed. I agree it's not 
>> a fundamental force like gravity or electromagnetism, but it 
>> is necessary to keep the system in equilibrium, otherwise 
>> what would be holding the satellite at a constant distance 
>> while it is being pulled towards earth? 
>> 
>> Example: a car is moving at 1m/s. You stand still on the 
>> driveway (your
>> speed: 0m/s.) The car hits you. Because the car is much 
>> heavier (err: has more mass) than you, you now move at close 
>> to 1m/s and the car has just slowed down a bit (m * v stays 
>> the same). The car has exerted a force on you that gave you 
>> acceleration. You have exerted a force on the car that caused 
>> the car to change it's speed, you imparted on the car a 
>> certain acceleration in the opposite direction. The only way 
>> the car could feel acceleration is because a force was 
>> exerted upon it. The force that was exerted on the car came 
>> from the inertia of your body. It is a real force. Now, 
>> imagine the driveway was itself on a sliding plane moving at 
>> 1m/s in the opposite direction to the car. In fact, the car 
>> was not moving but you were. It makes no difference, once you 
>> realize the only difference is where the reference it. Two 
>> forces were developed. Which one you call action and which 
>> one is reaction is irrelevant. It's only a matter of 
>> reference. Because you change the reference does not make the 
>> force go away.
>> 
>> We agree on what is happening, we don't agree on what to call it. 
>> 
>> Since you know a lot more about this than I do, I will accept 
>> your statement that centrifugal forces (or more generally 
>> inertial forces) are fictitious, but only because you insist. 
>> As long as I can predict their effect and calculate their 
>> magnitude, that's all this engineer is interested in :-)
>> 
>> 73,
>> Didier KO4BB
>> 
>> 
>> -----Original Message-----
>> From: time-nuts-bounces at febo.com 
>> [mailto:time-nuts-bounces at febo.com] On Behalf Of Ulrich Bangert
>> Sent: Monday, May 28, 2007 8:23 AM
>> To: 'Discussion of precise time and frequency measurement'
>> Subject: Re: [time-nuts] FW: Pendulums & Atomic Clocks & Gravity
>> 
>> Didier,
>> 
>> let us consider the more easier case of an linear motion. 
>> Imagine an body that can glide on an surface without any 
>> friction. Now you take a finger of your hand and press it on 
>> one side of the body so that it moves horizontally. Clearly 
>> your finger exercises an force on the body that makes it 
>> accelerate. And in your finger you feel an force into the 
>> opposite direction. 
>> 
>> The key question is about the physical reality of this force 
>> in the opposite direction. 
>> 
>> How big is it? I guess, you would argument that it has the 
>> same magnitude as the force that you apply with your finger 
>> but has the opposite direction, right? Now you have TWO 
>> forces. If they have the same magnitude but opposite 
>> direction their vectors add to zero and I am almost sure you 
>> would argument that this makes the sum of forces zero for the system.
>> 
>> Now, that you have shown that the sum of forces is zero you 
>> are in the ungraceful position in that you must explain why 
>> the body IS ACCELERATING at all. According to F=m*a a 
>> non-zero F is necessary to generate a non-zero a. How do you explain? 
>> 
>> Please note that in physics there is one substantial thing 
>> that one must know about forces and counterforces: They never 
>> affect on the SAME body but always on DIFFERENT bodies. In 
>> case you do not believe take the next textbook and read it 
>> after. For the above experiment this means: Since BOTH forces 
>> that you are talking about affect on the same one body one of 
>> the forces CANNOT be the counterforce to the other. If this 
>> is so then lets search for the counterforce for the force 
>> that you apply with your finger. In order to be able to 
>> execute this force your feet or other parts of your body 
>> execute an force into opposite direction to the surface of 
>> earth. These two forces are counterforces to each other because they
>> 
>> a) have opposite directions
>> 
>> b) have same magnitude
>> 
>> c) apply to different bodies.
>> 
>> Now that we have found the counterforce that makes the sum of 
>> forces zero for the system you need to find the counterforce 
>> to your inertial force and you will find none. Perhaps it is 
>> helpful for your understanding that one of the definitions 
>> for fictitious forces is that no counterforce belonging to 
>> them can be found. And if no counterforce can be found they 
>> have NO physical reality because otherwise the rule of the 
>> sum of forces is violated.
>> 
>> There was only ONE force F acting on the body that make it 
>> accelerate according F=m*a and this force had its source in 
>> your finger. To be able to execute this force you "pressed 
>> against earth" into the opposite direction and that makes the 
>> sum of forces zero. This is the only correct physical 
>> explanation of this example. ALL forces due to effects of 
>> inertia are fictitious forces.
>> 
>> 73 and my best regards
>> Ulrich, DF6JB
>> 
>> P.S.
>> 
>> Newton's first law says that a body at which all forces 
>> compensate keeps it current state of motion. To keep the 
>> current state of motion a body 
>> 
>> a) has to keep its velocity
>> 
>> and
>> 
>> b) has to keep its direction of flight.
>> 
>> It this what a satellite does? No, it permanently changes its 
>> direction of flight due to earth's gravitational force. If 
>> there were compensating forces the satellite would move away 
>> along a straight line.
>> 
>> Please note: I knew before that this would make a big 
>> discussion because the misconception is spread that wide. 
>> Perhaps you even learned this at school. When I worked as an 
>> "Wissenschaftlicher Mitarbeiter" (comparable to an assistent 
>> professor) at the department of physics of the German 
>> university at Bochum such miconceptions were one of our 
>> favourite subsects of study in teaching physics.  
>>    
>> 
>> 
>> 
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