Another Science Wager: Mehdi (ElectroBOOM) vs Steve Mould

[sandalcandal]

Another fun and interesting science/physics debate in a similar vein to the to the Derek Muller (Veritasium) vs Jack Goodman one on a faster than windspeed vehicle. This time for 10 000... cents.





"Original" Cambridge Video on Mould Effect:

Cambridge paper on Chain Fountain
Cambridge paper on Falling Chain Speed

I think Mehdi is correct with the idea that "the effect" is mostly related to momentum. Though I think the leverage phenomenon could be present and cause some minor contribution.

With the practical experiments (as it seems as is often the case) the physicists appear to have not fully considered non-ideal effects causing friction and other losses which can have an overriding effect in some of the practical setups; whereas the engineer has.

I haven't read/watched the Cambridge material yet. I would have thought a momentum or energy based equation for the maximum ideal "height" the fountain reaches to be fairly straight forward.

There also seems to be a bit of muddiness on what exactly "the effect" is defined as.

I'm sure there are people here with good grasps of kinematics that would also have opinions to weigh in.

[thm_w]

If they are claiming its due to leverage, can't you make a ball chain out of string and if its reproduced this disproves their paper.

edit: ok he basically does this at the end. Although I think the lead weights are maybe too heavy and spaced further apart than the ball chain, that might make some difference.

[DH7DN]

I guess the main difficulty is to set up a "clean" experiment under well defined conditions. The friction part of the conducted experiments is non-trivial.

I doubt there will be an analytic model for this phenomenon because the experiment itself has too many degrees of freedom. Nevertheless, the given equations from Cambridge papers give us a rough estimate for a certain case (rigid rod model) - maybe it can be simulated numerically (they tried but weren't able to establish a quantitative comparison).

Interesting phenomenon though! A "chain model" or "mass-spring-model" was very fruitful in solid state physics. It could explain the propagation of acoustic waves in solid bodies. Maybe a refined version of this chain model will be able to explain some complex flow phenomena such as pouring of a polymer (as shown by Mould).

I wonder if this has some applications in electronics, where you could accelerate a chain of charges and measure the Mould Effect in the EM-spectrum (accelerated charges emit radio waves) 

[sandalcandal]

New follow up from Steve

Those simulations are great.
Seems more like Reddit users proving Steve's point for him

[sandalcandal]

It continues

Looks like he didn't address the simulations Steve showed. Again, the most convincing evidence comes from viewers.

[ve7xen]

Given Mehdi's latest video, I actually think both are describing different aspects of the same thing. Limited bend radius as Mehdi explains describes the resulting geometry, but it doesn't provide any reasoning about how the forces are transferred in the system to realize that geometry. In my view, I'm not convinced by Mehdi that the countering force is negligible. In most of Mould's tests it seems quite pronounced, overcoming friction and clearly moving the entire pile of chain along the floor. Add the simulations that Mould's viewers did and it becomes more convincing. Even Mehdi's own 'tubular' apparatus is clearly shaking as the chain whips back and forth, so energy transfer to/from the support is definitely going on.

Intuitively to me, it seems that where the chain/rope curves away from the 'floor', there must be a downward force because of the limited bend radius and the rope naturally 'wanting' to exceed it and move directly in the most efficient direction.

Very interesting discussion.

[sandalcandal]

It continues yet more

[sandalcandal]

And the conclusion!