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

Didier Juges didier at cox.net
Mon May 28 19:45:00 EDT 2007

```Ulrich Bangert wrote:
> Didier,
>
>
>> 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.
>
>
Well, I want to understand, but your explanations are not satisfactory.
They support your point but are not an explanation for my observations.

When an object slides on the surface of a table, friction slows it down.
As the object slows down, the supporting table is pushed in the
direction of motion of the object. The force of inertia (the reluctance
of the object to change it's state of motion) pushes the table through
friction. Otherwise, where is the force that is pushing the table coming
from?

Newton's first law, the way I understand it, says that objects resist
changes to their state of motion. If they do not do it through force,
how do you know? Do they turn red and all upset and start yelling like
someone I know?

Now, there is something else I would be missing under your scenario.
When an object is subjected to acceleration, it gains speed. The product
of force by speed is stored in the object in the form of kinetic energy.
If the satellite is constantly being subjected to unbalanced forces and
falls, it should be accelerating and accumulating energy, yet it does
not. 10 years later, a satellite has no more kinetic energy than when it
was launched (if all goes well...) Actually, satellites that are in
elliptical orbits trade kinetic energy for potential energy, just like
the old L-C network constantly trades electrostatic energy for magnetic
energy. But the sum remains constant, except for friction on imperfect
vacuum of space.

So what is it that prevents the satellite that is constantly subjected
to unbalanced forces to not gain speed and energy?

>> 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?
>
>
The counterforce is precisely what makes the body resistant to change.
> 73s and my best regards
> Ulrich, DF6JB
>

Keep trying, I am sure eventually it will make sense...

73,
Didier KO4BB

```