"g" paradox...

[sm0ky2]

great topic. i love puzzles that make you use your mind..


first we must remember that gravity is an accellerating force, not a constant velocity.
there is a slight time delay between the time the stick begins to move, and the moment of inertia of the (non attached) objects resting on top of said stick is overcome. Thus the stick has a head start before the experiment begins. add in leverage / inbalanced center of mass, and the result is what we see in the experiments. notice that at the approximate center of mass, both stick and object are moving at almost the same rate, and towards the fixed end of the stick, the objects never leave the stick at all.






With milkovic's pendulum drive - this is a completely different thing all-together.  The free rolling ball converts most of its energy into kenetic impact against the motionless cart.

When the ball is attached to the pendulum: momentum is conserved, except for the moment when the force on the ball changes direction. during this moment, the force is straight ahead pushing the cart forward. Momentum is still conserved.
This is exactly how his 'water-pump' functions.
no doubt that a pendulum is one of the most efficient devices for converting potential to kenetic energy and back again.
take for example a BOX on a RAMP...
compare this now to a ROLLER SKATE on the SAME RAMP..
you will see that the roller skate is much more efficient at rolling down the ramp. this is no different.

What these two 'problems' have in common, is that people often fail to look at all the factors involved. and even at times intentionally leave out factors that their audience deserves to know about.
While these things may seem strange when presented behind a fogcover, they are certainly not a 'paradox' by any definition of the word.

[iacob alex]

...as I see the things,is more related to MT18,than to MT25.

   "g " paradox (as the people gives the name on net) is interesting because introduces the "whip" effect:an elastic falling stick,as a new lab-demo...

   On net,you can find something alike with the label "falling chain".

   For PM,this phenomenon is useful to take into account for some designs...

    All the Best! / Alex

[iacob alex]

.....can be seen  as a possible paradox (something that seems absurd,but may be true) ,or as a real effect of  mass distribution ,when the free falling object is attached to a hinge.

     Let's see again the stick (continuous,rigid mass) and the coins ( disperse,bending mass),in a hinged free fall at :   http://www.youtube.com/watch?v=NFJPQLhWPvA

     If the stick and the coins have the same mass,and repeating the test,we get the same result/effect ,we have an interesting case,maybe useful for the topic of this forum.

     Anyway,all experiments of PM (on paper or in reality ),have as a "leitmotiv" ,the left-right replacement,change of distribution of the same mass...

       All the best! / Alex

[iacob alex]

.....can be a simple and apparently lab-demo "trick" (unequally masses and differently starting point/height).

      But it can be also,a convincing,simple fact of reality,if we repeat the Galileo's easy experiment,this time with two equally,identically masses that fall from the same elevation,starting in the same moment:

        -mass A falls vertically,on a straight line.

        -mass B falls on a different trajectory...let's say as a free falling inverted pendulum.

     If there is a time (velocity,momentum...) difference,we have an "entrance" to think about the next step(s)...

        All the best! / Alex

[Dr]

HI Alex: very nice demonstration, I also read your thoughts about the long arm short arm pendulum, and i must say I think you are right on the money. If a gravity wheel is to work, the weights must not move a great deal... long arm of a horizontal pendulum falling from around 2:45 position and swinging over to the 9:00 O clock position, it is there when CF has released some of its grip that the shift must occurr.