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Newton's third law problem.

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electrodacus:

--- Quote from: PlainName on November 28, 2022, 12:05:10 am ---
And yet the videos showed them accelerating. Must've been accumulating energy for storage, eh.


--- End quote ---

Do you understand what decrease acceleration rate means ?
That video is poorly done and does not show actually anything.

Every time the vehicle body is connected to ground either through a device or the hand of the experimenter the energy storage is being charged.
So there are only very brief moments where vehicle is shown discharging the energy storage.
Once you understand all elements involved you will understand why this is a poorly done experiment.

The one done by Derek (Veritasium) was much better and they could have measured the decrease in acceleration rate by taking a video from the moment of release until vehicle left the treadmill and then calculate from the video frames what the acceleration rate was for the first half of the run and the second run showing clearly that acceleration rate drops as stored energy is being used up.
Based on that they could have calculated how far the vehicle will have traveled before it stopped accelerating and then how long it will have took for the vehicle speed to drop to zero.
So no need for a very long treadmill to make measurements and show what happens.
Another way to deal with a limited length treadmill was to increase the vehicle mass as then max speed will have been much lower and so the distance traveled.
But nobody even looked for this as they all assumed vehicle will forever drive in the opposite direction of the force applied (ridiculous to think if you understand the basics of classical mechanics).
The professor that lost the bet understood that this is not possible thus his high confidence. Unfortunately he did not know how the vehicle actually works and that energy storage was involved. 

IanB:

--- Quote from: electrodacus on November 28, 2022, 12:40:38 am ---But nobody even looked for this as they all assumed vehicle will forever drive in the opposite direction of the force applied (ridiculous to think if you understand the basics of classical mechanics).
--- End quote ---

If you sling a rope over a pulley and pull downwards, the weight on the other end will get pulled upwards (the opposite direction of the force applied). This is ridiculous to think if you understand the basics of classical mechanics, so we have to assume that pulleys can only work by stored energy and stick-slip hysteresis.

electrodacus:

--- Quote from: IanB on November 28, 2022, 01:59:36 am ---
If you sling a rope over a pulley and pull downwards, the weight on the other end will get pulled upwards (the opposite direction of the force applied). This is ridiculous to think if you understand the basics of classical mechanics, so we have to assume that pulleys can only work by stored energy and stick-slip hysteresis.

--- End quote ---

Pulley in order to work will have 3 points of contact the input the output and the center of the pulley all have a connection to something.
The vehicle used as example for upwind has only input and output connected the body is floating.

It is like you connecting the positive input of a DC-DC converter to battery+ the negative of the battery is connected to earth the positive output of the DC-DC converter to earth and the negative input and output of the DC-DC converter connected to each other but nothing else and you expecting that DC-DC converter to do anything useful.

Kleinstein:

--- Quote from: electrodacus on November 28, 2022, 02:29:29 am ---
It is like you connecting the positive input of a DC-DC converter to battery+ the negative of the battery is connected to earth the positive output of the DC-DC converter to earth and the negative input and output of the DC-DC converter connected to each other but nothing else and you expecting that DC-DC converter to do anything useful.

--- End quote ---

That configuration is a little unusual, but can still work if the DC/DC converter has a lower output than input voltage and can thus provide more current at the output than it needs at the input. It is not a very praktical (efficient) solution but it would still generate a negative voltage. With real world parts it may need so help to start up, depending how well the DCDC converter handles load to the output if there is no input drive.

cbutlera:

--- Quote from: Kleinstein on November 28, 2022, 08:38:51 am ---
--- Quote from: electrodacus on November 28, 2022, 02:29:29 am ---
It is like you connecting the positive input of a DC-DC converter to battery+ the negative of the battery is connected to earth the positive output of the DC-DC converter to earth and the negative input and output of the DC-DC converter connected to each other but nothing else and you expecting that DC-DC converter to do anything useful.

--- End quote ---

That configuration is a little unusual, but can still work if the DC/DC converter has a lower output than input voltage and can thus provide more current at the output than it needs at the input. It is not a very praktical (efficient) solution but it would still generate a negative voltage. With real world parts it may need so help to start up, depending how well the DCDC converter handles load to the output if there is no input drive.

--- End quote ---

I just tried it with an old Traco TEF2011 module that I found in my junk box, 10-30V in 5V out.  It needed an additional 5V power supply connected to the output to get it started, but once started the additional supply could be disconnected.  As expected it worked just fine, and even continued to run with the input power supply reduced to 2V, giving 7V across the converter input terminals.

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