Author Topic: Newton's third law problem.  (Read 18719 times)

0 Members and 2 Guests are viewing this topic.

Offline bdunham7

  • Super Contributor
  • ***
  • Posts: 7729
  • Country: us
Re: Newton's third law problem.
« Reply #175 on: November 27, 2022, 10:08:05 pm »
One link shows the equation the other is a calculator using that equation and that equation will provide you with any question you may have about power needed to overcome drag when driving upwind and it can also calculate the max wind power available to vehicle when driving downwind.

Nope, every word of that is entirely wrong.
A 3.5 digit 4.5 digit 5 digit 5.5 digit 6.5 digit 7.5 digit DMM is good enough for most people.
 

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Newton's third law problem.
« Reply #176 on: November 27, 2022, 10:10:57 pm »

Nope, every word of that is entirely wrong.

That is your unqualified opinion.  You will need to measure and prove it is not true assuming you even understand what you will need to measure and 3.5 digit will be enough :)

Online PlainName

  • Super Contributor
  • ***
  • Posts: 6796
  • Country: va
Re: Newton's third law problem.
« Reply #177 on: November 27, 2022, 10:23:31 pm »

a) How did you derive those terms? You could post anything and say that's correct, or copy anything and say it's correct "because someone else uses it too", but unless you know how the terms were derived it's meaningless to you.

b) Which term(s) cover the propeller and wheel operation? The propeller, and connection to the wheels, is kind of super-important since it's the thing that makes it work, and yet it doesn't exist in your copied equation. How can that equation possibly account for it, then?

a) not only I know how that is derived but also know it is correct as I build things not just play with numbers.

So tell us then. Show us your workings so we can go "Doh! Of course, now we can see it."

Quote
b) The equation for available wind power to any wind power vehicle is independent of the design other than shape and area interacting with air particles.
The wheel propeller connection is a separate issue ...

It isn't a separate issue. Consider two scenarios:

1. The propeller blades are perpendicular to the wind. In this case the propeller might as well be a flat surface with area the same as the blades, and the power sucked from the wheel (if that's what you think happens) will be near enough zero.

2. The propeller blades are parallel to the wind. In this case the propeller is more or less non-existent so far as the wind pressure is concerned, but it is sucking maximum power from the wheels.

How can you say it's irrelevant when it can affect the system so much?
 

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Newton's third law problem.
« Reply #178 on: November 27, 2022, 10:48:30 pm »
Quote
b) The equation for available wind power to any wind power vehicle is independent of the design other than shape and area interacting with air particles.
The wheel propeller connection is a separate issue ...

It isn't a separate issue. Consider two scenarios:

1. The propeller blades are perpendicular to the wind. In this case the propeller might as well be a flat surface with area the same as the blades, and the power sucked from the wheel (if that's what you think happens) will be near enough zero.

2. The propeller blades are parallel to the wind. In this case the propeller is more or less non-existent so far as the wind pressure is concerned, but it is sucking maximum power from the wheels.

How can you say it's irrelevant when it can affect the system so much?

1 and 2.  Do you even read what I write ?
"independent of the design other than shape and area interacting with air particles"

I see your interest is in the direct downwind faster than wind vehicle and blackbird to be specific as the same thing can be done without any propeller and in that case the propeller is
a) a sail with increasingly large effective area as the rotational speed increases.
b) propulsion device
c) part of the energy storage device.


The discussion here is much more basic and asks the amount of wind power available to any wind powered vehicle. All you need to know about vehicle design is shape (so drag coefficient) and vehicle area facing the wind.
You seems to disagree with that based on your false impression that above wind speed direct downwind blackbird is powered by wind (not the case).
While blackbird is above wind speed it is powered by stored energy only. And yes that means acceleration rate will drop if you can not control the rate at witch you use that stored energy. With the blackbird you can control that as pilot can change the propeller pitch. The treadmill model has no pitch control so on that it will be very easy to observe decrease in acceleration rate as stored energy is used up.

Online PlainName

  • Super Contributor
  • ***
  • Posts: 6796
  • Country: va
Re: Newton's third law problem.
« Reply #179 on: November 28, 2022, 12:05:10 am »
Quote
The treadmill model has no pitch control so on that it will be very easy to observe decrease in acceleration rate as stored energy is used up.

And yet the videos showed them accelerating. Must've been accumulating energy for storage, eh.

« Last Edit: November 28, 2022, 12:09:06 am by PlainName »
 

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Newton's third law problem.
« Reply #180 on: November 28, 2022, 12:40:38 am »

And yet the videos showed them accelerating. Must've been accumulating energy for storage, eh.


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. 

Offline IanB

  • Super Contributor
  • ***
  • Posts: 11790
  • Country: us
Re: Newton's third law problem.
« Reply #181 on: November 28, 2022, 01:59:36 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).

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.
 

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Newton's third law problem.
« Reply #182 on: November 28, 2022, 02:29:29 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.

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.
« Last Edit: November 28, 2022, 02:31:02 am by electrodacus »
 

Offline Kleinstein

  • Super Contributor
  • ***
  • Posts: 14080
  • Country: de
Re: Newton's third law problem.
« Reply #183 on: November 28, 2022, 08:38:51 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.

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.

 

Offline cbutlera

  • Regular Contributor
  • *
  • Posts: 104
  • Country: gb
Re: Newton's third law problem.
« Reply #184 on: November 28, 2022, 09:15:30 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.

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.

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.
 

Offline Circlotron

  • Super Contributor
  • ***
  • Posts: 3168
  • Country: au
Re: Newton's third law problem.
« Reply #185 on: November 28, 2022, 11:03:15 am »
If you apply no power the vehicle will be accelerated in the direction of the wind and you need to match that power in ideal case to stay at zero speed then you need extra in order to move upwind.
If you are staying at zero speed then no work is being expended. A force maybe, but if there is no movement then no power is being used.
 

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Newton's third law problem.
« Reply #186 on: November 28, 2022, 04:56:20 pm »

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.

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.

Did you understood the setup ?
There are only to points connected on the DC-DC converter. The positive input and the positive output and nothing else.
Can you explain how you will get higher current at output than at the input ?

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Newton's third law problem.
« Reply #187 on: November 28, 2022, 05:01:10 pm »

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.

Sorry but can you be more exact in describing your setup ?
You can of course have a voltage drop on the converter if you have a current flowing through the converter depending on the type of converter.
What you can not have is a higher voltage at output than input, a negative voltage or different current at output than at the input.

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Newton's third law problem.
« Reply #188 on: November 28, 2022, 05:07:21 pm »
If you are staying at zero speed then no work is being expended. A force maybe, but if there is no movement then no power is being used.

Have you ever had an electric motor providing a force / torque without using energy ? Or even simpler an electromagnet providing a force without using energy.
Even you using your arm to provide a force will be using energy even tho there is no movement and yes that energy will be dissipated as heat.
 

Offline Kleinstein

  • Super Contributor
  • ***
  • Posts: 14080
  • Country: de
Re: Newton's third law problem.
« Reply #189 on: November 28, 2022, 05:14:55 pm »

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.

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.

Did you understood the setup ?
There are only to points connected on the DC-DC converter. The positive input and the positive output and nothing else.
Can you explain how you will get higher current at output than at the input ?

The effective input voltage see by the DC/DC converter is the sum of input voltage + output voltage (not considering a sign). So the available output current / load current between the DCDC converters outputs is the difference of the input current minus the output current.  So if the DCDC converter is something like a 24 V input to 6 V output type  with 75% efficiency one would have 3 times the ouput courrent at the DCDC converter an 2 times the output current from the input current. So one could get something like 18V 1A in and -6 V 2 A out.

There is nothing magic with the circuit - depending one the DCDC is may just need some help on start up.
 

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Newton's third law problem.
« Reply #190 on: November 28, 2022, 05:23:32 pm »
The effective input voltage see by the DC/DC converter is the sum of input voltage + output voltage (not considering a sign). So the available output current / load current between the DCDC converters outputs is the difference of the input current minus the output current.  So if the DCDC converter is something like a 24 V input to 6 V output type  with 75% efficiency one would have 3 times the ouput courrent at the DCDC converter an 2 times the output current from the input current. So one could get something like 18V 1A in and -6 V 2 A out.

There is nothing magic with the circuit - depending one the DCDC is may just need some help on start up.

Maybe I need to be more clear as I do not think you understood the setup.
Get a plastic box and put in it whatever you want as long as it is not an energy source like a battery. So you can put a DC-DC converter inside.
The box will have just two wires one on each end and nothing else.
Now can you have a difference in current between the two wires ?  Have you ever seen a two pin IC that could have a current input at one of the pins and a different current on the other pin.

Offline cbutlera

  • Regular Contributor
  • *
  • Posts: 104
  • Country: gb
Re: Newton's third law problem.
« Reply #191 on: November 28, 2022, 05:36:12 pm »

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.

Sorry but can you be more exact in describing your setup ?

The setup was exactly and precisely the one that you described, other than the temporary connection of a second power supply across the output terminals of the DC/DC converter to get the thing started.  Once started the second power supply was disconnected.

Quote
You can of course have a voltage drop on the converter if you have a current flowing through the converter depending on the type of converter.
What you can not have is a higher voltage at output than input, a negative voltage or different current at output than at the input.

The output voltage was not higher than the input.  The output of the DC/DC converter was 5V.  The external power supply, set to 2V, was connected between the input and output of the DC/DC converter just as you described, which boosted this voltage to 7V. So there was 7V at the input to the DC/DC converter.

The input current and output current are necessarily equal.  With no load, the circuit naturally settles at an operating current such that the 2V boost to the output voltage exactly compensates for the losses in the DC/DC converter.

This experiment took less than 10 minutes to perform.  Rather than arguing about it, please just try it for yourself.
 

Offline james_s

  • Super Contributor
  • ***
  • Posts: 21611
  • Country: us
Re: Newton's third law problem.
« Reply #192 on: November 28, 2022, 05:47:36 pm »
This experiment took less than 10 minutes to perform.  Rather than arguing about it, please just try it for yourself.

You expect a troll to try an experiment? He just got you to waste your time setting one up, and he's going to continue to argue that it can't work despite the fact that it does.
 
The following users thanked this post: PlainName, cbutlera

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Newton's third law problem.
« Reply #193 on: November 28, 2022, 05:49:24 pm »

The setup was exactly and precisely the one that you described, other than the temporary connection of a second power supply across the output terminals of the DC/DC converter to get the thing started.  Once started the second power supply was disconnected.


The output voltage was not higher than the input.  The output of the DC/DC converter was 5V.  The external power supply, set to 2V, was connected between the input and output of the DC/DC converter just as you described, which boosted this voltage to 7V. So there was 7V at the input to the DC/DC converter.

The input current and output current are necessarily equal.  With no load, the circuit naturally settles at an operating current such that the 2V boost to the output voltage exactly compensates for the losses in the DC/DC converter.

This experiment took less than 10 minutes to perform.  Rather than arguing about it, please just try it for yourself.

The setup was surely not as I asked.
But let me simplify things and make it even simpler to understand.
You get a plastic box and put whatever you want in the box as long as there is no energy source like a battery.
And out of that box you have two wires and nothing else.

Now what you say is that you will put a DC-DC converter in that box and get the positive input and positive output out of that box.
My understanding will be that you connected the positive input to your lab power supply positive output and the positive output of the DC-DC converter to the negative of your lab power supply.
But then it will not make sense to say you measured 7V if the lab power supply was set to 5V. Where will you measure 7V ?
I may guess you charged some large capacitor on the DC-DC converter and then you measured that in series with your lab power supply voltage.

So the plastic box with just two wires coming out seems a better simplification and you can get inside whatever you want.  You will not be able to have a different current through one of the two wires.

Offline fourfathom

  • Super Contributor
  • ***
  • Posts: 1851
  • Country: us
Re: Newton's third law problem.
« Reply #194 on: November 28, 2022, 06:20:13 pm »
I think you guys should get back to wheels, gears, and surfaces.  Misunderstood switching regulator topology when the model doesn't even represent the thing being analyzed is getting you nowhere.

Or, DDWFTTW: The cart wheels drive a generator, the generator powers a fan blowing backwards.  To start, the wind pressure gives the idle fan a little push.  The cart starts rolling downwind, spinning the generator which powers the fan.  Take it from there.  But remember the wheels rolling on the ground.  For starters, assume no slip, no energy storage, no friction, no loss.

And while interesting, I realize that this discussion is a lost cause.  Fortunately for me, I enjoy some lost causes.
We'll search out every place a sick, twisted, solitary misfit might run to! -- I'll start with Radio Shack.
 

Offline IanB

  • Super Contributor
  • ***
  • Posts: 11790
  • Country: us
Re: Newton's third law problem.
« Reply #195 on: November 28, 2022, 06:36:10 pm »
Classic troll behavior. When losing the debate on the original problem, come up with some entirely different problem as a distraction, and try to argue that. And when that argument doesn't go well, keep trying to move the goalposts in order to get the conclusion desired. And than try to say that any conclusion drawn from the entirely different problem must also apply to the original problem.
 

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Newton's third law problem.
« Reply #196 on: November 28, 2022, 06:39:23 pm »

Or, DDWFTTW: The cart wheels drive a generator, the generator powers a fan blowing backwards.  To start, the wind pressure gives the idle fan a little push.  The cart starts rolling downwind, spinning the generator which powers the fan.  Take it from there.  But remember the wheels rolling on the ground.  For starters, assume no slip, no energy storage, no friction, no loss.


You do realize you try to describe an overunity device ? If vehicle is direct down wind aboe wind speed.
Wind pushes the vehicle so instead of leaving it at that you brake the vehicle to extract energy at the wheel than then you put in to the propeller to get at best about 70% back in to propulsion.

What happens is as you describe when vehicle starts and that is the vehicle is pushed by wind same as any sail vehicle then instead of using all that to accelerate the vehicle you take a big part of the energy at the wheel and use the propeller to create a pressure differential (basically store that energy).

So if you have 1000W available as wind power you use say only 200W to accelerate the vehicle while taking the other 800W at the wheel and due to efficiency maybe put around 500W in storage so after 1ms of this you get to store about 0.5Ws
As vehicle accelerates the amount of wind power available from wind drops but the amount provided by the stored energy increases and this allows vehicle to get to a speed well above wind speed but then after stored energy is used up it will slow down below wind speed.

I think a simple vehicle to understand that will do exactly the same thing will be:

A simple sail vehicle with an electrical generator at the wheel so when vehicle is well below wind speed you can charge a supercapacitor or a battery but a supercapacitor will be sufficient then after some seconds when you consider enough energy was stored you can accelerate direct downwind for as long as you have stored energy. So you can do a fast acceleration to say 2x the wind speed maybe in 30 seconds or you can do a very slow acceleration say over 5 minutes to same 2x wind speed but in both cases you only have enough energy to accelerate the vehicle to that peak speed as energy stored in supercapacitor is converted in vehicle kinetic energy.
And from that peak speed say 2x the wind speed it will again take a few minutes to slow down to wind speed depending on the amount of friction losses vs the amount of gained kinetic energy.

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Newton's third law problem.
« Reply #197 on: November 28, 2022, 06:45:48 pm »
Classic troll behavior. When losing the debate on the original problem, come up with some entirely different problem as a distraction, and try to argue that. And when that argument doesn't go well, keep trying to move the goalposts in order to get the conclusion desired. And than try to say that any conclusion drawn from the entirely different problem must also apply to the original problem.

Sorry I must have missed the part where you demonstrated that the equation for available wind power was wrong ?

If you want to say I lost the argument then you need to show proof the equation everyone is using is wrong.

So show the output from this free online calculator is not corresponding with real world experiments  https://www.electromotive.eu/?page_id=12&lang=en
If you can do that I will admit to be wrong and apologize to everyone.

If not that equation alone is enough to prove that this sort of vehicle's do not work as you claim and most certainly work the way I explain and guaranteed they use energy storage.

Online PlainName

  • Super Contributor
  • ***
  • Posts: 6796
  • Country: va
Re: Newton's third law problem.
« Reply #198 on: November 28, 2022, 07:13:50 pm »

Or, DDWFTTW: The cart wheels drive a generator, the generator powers a fan blowing backwards.  To start, the wind pressure gives the idle fan a little push.  The cart starts rolling downwind, spinning the generator which powers the fan.  Take it from there.  But remember the wheels rolling on the ground.  For starters, assume no slip, no energy storage, no friction, no loss.


You do realize you try to describe an overunity device ?

Of course it isn't - there are limits to how much it works. The many practical examples should have shown that it does work, it's just that with your closed and single-track mind you'll never grasp it. Perhaps you're afraid of doing so after all the nay saying you've staked your reputation on (what little of it remains).
 

Offline electrodacusTopic starter

  • Super Contributor
  • ***
  • Posts: 1858
  • Country: ca
    • electrodacus
Re: Newton's third law problem.
« Reply #199 on: November 28, 2022, 07:20:53 pm »
Of course it isn't - there are limits to how much it works. The many practical examples should have shown that it does work, it's just that with your closed and single-track mind you'll never grasp it. Perhaps you're afraid of doing so after all the nay saying you've staked your reputation on (what little of it remains).

There is a simple question.

What is the wind power available to a wind powered vehicle ?

My answer (and not just mine) is this https://scienceworld.wolfram.com/physics/DragPower.html

That equation alone is what proves "your" explanation of how this vehicle's work wrong.

All you need to do to prove me wrong is do an experiment that shows that equation is incorrect.


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf