Author Topic: Newton's third law problem.  (Read 18525 times)

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Offline IanB

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Re: Newton's third law problem.
« Reply #150 on: November 25, 2022, 05:23:16 am »
It could fly if the friction is high enough or the acceleration rate of the treadmill is large enough.

Don't be absurd.

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The point is the body is floating.

No, the point is that it is fixed on a horizontal plane and is not free to rotate.

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There is no law of physics that says this.

It is for this particular gearbox configuration as it is locked basically no different from a rock


Saying that it is locked is a conclusion reached before doing the analysis. It is clearly not locked, since it has all sorts of axles and freely rotating wheels and belts. It would only be locked if it had brakes, and there are no brakes in the model. The wheels are free to turn.

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Just like car's gearbox then? It has the input connected to the engine, the output to the road, and the body not connected to anything? And yet, somehow, the gearbox in a car works.

The car gearbox body is connected to the motor stator or engine body.
It is like the treadmill body was connected to this vehicle body instead of the ground.

This is meaningless. No clue what you are trying to say.

Anyway, good night. We will see tomorrow if anybody else feels like playing with the troll.
 

Offline electrodacusTopic starter

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Re: Newton's third law problem.
« Reply #151 on: November 25, 2022, 05:38:00 am »
Don't be absurd.

No, the point is that it is fixed on a horizontal plane and is not free to rotate.

Saying that it is locked is a conclusion reached before doing the analysis. It is clearly not locked, since it has all sorts of axles and freely rotating wheels and belts. It would only be locked if it had brakes, and there are no brakes in the model. The wheels are free to turn.

This is meaningless. No clue what you are trying to say.

Anyway, good night. We will see tomorrow if anybody else feels like playing with the troll.

You mentioned forces come in pairs.
The only force pair is F1 relative to ground not relative to vehicle body.
So vehicle/gearbox has input connected to F1 and output to ground and nothing else.

I should have insisted more on the floating gearbox as it seems it was not obvious.

Offline PlainName

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Re: Newton's third law problem.
« Reply #152 on: November 25, 2022, 10:29:13 am »
Quote from: IanB
Anyway, good night. We will see tomorrow if anybody else feels like playing with the troll

I admire your perseverance and composure in the face of insurmountable odds  :-+
 

Offline electrodacusTopic starter

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Re: Newton's third law problem.
« Reply #153 on: November 27, 2022, 01:33:08 am »
Don't be absurd.


Here a link to a proper vehicle physics calculator https://www.electromotive.eu/?page_id=12&lang=en
Just change the head wind to 100km/h leave all the rest as default (it is for an ebike) see what power is needed for the biker pedaling at 20km/h in a 100km/h headwind and is almost 20kW as they use the proper equation.

Offline Circlotron

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Re: Newton's third law problem.
« Reply #154 on: November 27, 2022, 08:16:59 am »
Here a link to a proper vehicle physics calculator https://www.electromotive.eu/?page_id=12&lang=en
That calculator is next to useless. It has no facility to include coefficient of drag so it doesn't know the difference between a teardrop shape and a box shape.
 

Offline wraper

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Re: Newton's third law problem.
« Reply #155 on: November 27, 2022, 09:11:03 am »
Here a link to a proper vehicle physics calculator https://www.electromotive.eu/?page_id=12&lang=en
That calculator is next to useless. It has no facility to include coefficient of drag so it doesn't know the difference between a teardrop shape and a box shape.
It has.
 

Offline Kleinstein

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Re: Newton's third law problem.
« Reply #156 on: November 27, 2022, 10:55:33 am »
That calulator is useless an using the wrong equations:  compare the case of 100 km/h headwind and 20 km/h with 110 and 10 and the calculator gives out the same result. The actual power needed would be half.
 

Offline fourfathom

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Re: Newton's third law problem.
« Reply #157 on: November 27, 2022, 03:29:49 pm »
And that calculator is irrelevant, or at least applicable to only a small part of the DDWFTTW discussion and that part can be ignored when studying the general principles. 

electro' still insists that the treadmill models are "transmission-locked" 
electro' still insists that his "wind turbine generator powering a motor that turns the wheels" is a valid analogy to the demonstrated DDWFTTW vehicles. 
Neither of these assertions is remotely true.

Pedaling bicycles upwind is a distraction that confuses rather than clarifies.
We'll search out every place a sick, twisted, solitary misfit might run to! -- I'll start with Radio Shack.
 

Offline electrodacusTopic starter

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Re: Newton's third law problem.
« Reply #158 on: November 27, 2022, 03:36:02 pm »
That calulator is useless an using the wrong equations:  compare the case of 100 km/h headwind and 20 km/h with 110 and 10 and the calculator gives out the same result. The actual power needed would be half.

The calculator actually uses the correct equation and the result will be the same for vehicle at 20km/h with 100km/h head wind as it will be for vehicle at 110km/h and just 10km/h head wind.

Not quite sure where the wrong equation many of you are using originated.  Can someone point to a source for that equation and I'm not referring to Wikipedia.
That wrong equation seems to have significant implications and I will like to get rid of it. Anyone that will do an actual experiment will realize the correct equation is the one I mentioned hundreds of times and also the same used in that calculator.

Here is another website with the correct equation and definition https://scienceworld.wolfram.com/physics/DragPower.html
it reads correctly as v being the speed of the fluid relative to the body (vehicle in this case). 

Offline electrodacusTopic starter

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Re: Newton's third law problem.
« Reply #159 on: November 27, 2022, 03:42:16 pm »
And that calculator is irrelevant, or at least applicable to only a small part of the DDWFTTW discussion and that part can be ignored when studying the general principles. 

electro' still insists that the treadmill models are "transmission-locked" 
electro' still insists that his "wind turbine generator powering a motor that turns the wheels" is a valid analogy to the demonstrated DDWFTTW vehicles. 
Neither of these assertions is remotely true.

Pedaling bicycles upwind is a distraction that confuses rather than clarifies.

The equation (correct one) used in that calculator is key to understand upwind version and also key to understand direct downwind version tho that will actually require even more understanding of fluid mechanics.
But I think once we can establish that is the correct equation (and there are relatively simple tests that can prove that is the case) there will be zero way to claim that direct upwind can happen without energy storage.
As that equation states that to move upwind you need more power than what is available to vehicle in ideal case from the wind.  Ideal case vehicle will be in equilibrium.

Offline fourfathom

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Re: Newton's third law problem.
« Reply #160 on: November 27, 2022, 03:55:18 pm »
there will be zero way to claim that direct upwind can happen without energy storage.
As that equation states that to move upwind you need more power than what is available to vehicle in ideal case from the wind.  Ideal case vehicle will be in equilibrium.

"And yet it moves."

Energy storage?  Think about it a bit.  If you can move upwind or downwind with energy storage, you can move upwind or downwind with sufficiently low gearing -- no storage required.  Storage is irrelevant and unnecessary.

And now I have hit my daily limit for this thread.
We'll search out every place a sick, twisted, solitary misfit might run to! -- I'll start with Radio Shack.
 

Offline electrodacusTopic starter

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Re: Newton's third law problem.
« Reply #161 on: November 27, 2022, 04:00:02 pm »

"And yet it moves."

Energy storage?  Think about it a bit.  If you can move upwind or downwind with energy storage, you can move upwind or downwind with sufficiently low gearing -- no storage required.  Storage is irrelevant and unnecessary.

And now I have hit my daily limit for this thread.

A gearbox can not amplify power.
If to drive upwind requires more power than available form the wind. How do you get the extra power if not from stored energy?

Offline Kleinstein

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Re: Newton's third law problem.
« Reply #162 on: November 27, 2022, 04:32:35 pm »
A gearbox can not amplify power.
If to drive upwind requires more power than available form the wind. How do you get the extra power if not from stored energy?

There is not need to have more power than the wind, it is only about having more force available than the wind.

With the wind much faster than the movement to ground the force from the wind is approximatedly constant. The power needed is just force times speed. So zero power at zero speed and little power needed at low speed.
The gearbox can not amplify power, but it can amplifiy the torque / force.
 

Offline electrodacusTopic starter

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Re: Newton's third law problem.
« Reply #163 on: November 27, 2022, 04:41:59 pm »

There is not need to have more power than the wind, it is only about having more force available than the wind.

With the wind much faster than the movement to ground the force from the wind is approximatedly constant. The power needed is just force times speed. So zero power at zero speed and little power needed at low speed.
The gearbox can not amplify power, but it can amplifiy the torque / force.

Vehicle will not need zero power to keep the vehicle at equilibrium point and zero speed.
You are thinking about having the vehicle anchored to ground by applying brakes but that just makes the entire earth part of the vehicle so no longer separated.
Please imagine a vehicle that has no brakes then think about the amount of power needed to keep the vehicle stationary based on wind speed and vehicle effective projected area facing the wind.
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.

Offline PlainName

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Re: Newton's third law problem.
« Reply #164 on: November 27, 2022, 06:49:13 pm »
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Not quite sure where the wrong equation many of you are using originated.  Can someone point to a source for that equation and I'm not referring to Wikipedia.

And yet it's OK for you to copy random equations from t'web to prove ... something. Why not actually write yours1 from scratch instead of copying someone elses thing meant for some different scenario? You might learn something.

---
[1] You don't seem to have made one yet. You've copypasta'd many.
 

Offline james_s

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Re: Newton's third law problem.
« Reply #165 on: November 27, 2022, 07:00:30 pm »
You might learn something.

Learning something is not the goal of trolling. He's obviously just yanking your chain, no real person is that stupid or dense.
 

Offline electrodacusTopic starter

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Re: Newton's third law problem.
« Reply #166 on: November 27, 2022, 07:05:46 pm »
And yet it's OK for you to copy random equations from t'web to prove ... something. Why not actually write yours from scratch instead of copying someone elses thing meant for some different scenario? You might learn something.

Not quite sure what you are talking about.  The equation is universal and is just one applicable to all of this cases.
You may make your own equations if you come up with new physics but there is nothing new in relation with what we discuss here.

The correct and universal equation for Drag Power is this that I mentioned for months here and all of you where disagreeing with.

Pd = 0.5 * air density * (area * coefficient of drag) * (wind speed - vehicle speed)3

The wrong equation that many of you are claiming to be correct is the one below,
 
Pd = 0.5 * air density * (area * coefficient of drag) * (wind speed - vehicle speed)2 * vehicle speed


Both this link https://scienceworld.wolfram.com/physics/DragPower.html  and this calculator https://www.electromotive.eu/?page_id=12&lang=en  use the correct equations so they agree with what I'm saying.
I provided those links to show that I'm not inventing new physics but that all this is known for a very long time.

« Last Edit: November 27, 2022, 07:08:41 pm by electrodacus »
 

Offline PlainName

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Re: Newton's third law problem.
« Reply #167 on: November 27, 2022, 07:18:41 pm »
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The correct and universal equation for Drag Power is this that I mentioned for months here and all of you where disagreeing with.

Pd = 0.5 * air density * (area * coefficient of drag) * (wind speed - vehicle speed)3

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?
 

Offline Kleinstein

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Re: Newton's third law problem.
« Reply #168 on: November 27, 2022, 07:28:23 pm »
The formular for the drag power is the frist one, but this is the power theoretical possible to take from the wind and that is not the power needed for the vehicle to drive. The power for the vehicle is more like the 2nd formular.

It is obvious that the first formula can not be corrent for the power of the vehicle: if the vehicle changes direction from going against the wind to going with the wind it changes from needing power to drive to gaining power from the wind. So the sign in the power has to change at around 0 vehicle speed.
Another way is to look at the force need: mechnical power is force times speed, more or less by definition. The force from the wind is limited and approaching zero speed the power this also has the approach zero.

The relevant question for the vehicle is if the motor can provide sufficient force. The power only determines how fast the vehicle can go. With low speed very little power is sufficient.
 

Offline bdunham7

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Re: Newton's third law problem.
« Reply #169 on: November 27, 2022, 07:29:11 pm »
Both this link https://scienceworld.wolfram.com/physics/DragPower.html  and this calculator https://www.electromotive.eu/?page_id=12&lang=en  use the correct equations so they agree with what I'm saying.
I provided those links to show that I'm not inventing new physics but that all this is known for a very long time.

You've scoured the internet to find 'examples' where someone has made an error somewhere that supports your argument, but those errors are painfully obvious with just a little bit of a fair-minded consideration.

In the Wolfram example, they clearly have only considered the case where the vehicle speed is the same as the speed of the fluid relative to the body, as in driving in still air.  That is obvious simply looking at the equations.

In your other example, if you bother to read their explanations elsewhere on their website under "Vehicle Physics" they say:

Now, the propulsion power can be calculated as a product of driving resistance and vehicle speed:

But from the operation of the malfunctioning calculator app, you can see that they have not incorporated this into their algorithm. 

In neither case do they use the equation you claim they do.

The Wolfram example has at least one part right before they go and screw it up.  P = FD * Vvehicle
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

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Re: Newton's third law problem.
« Reply #170 on: November 27, 2022, 07:54:25 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.
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 and using that data you can calculate how much of the available wind power is used to increase vehicle kinetic energy and how much is diverted to propeller witch will use it to store it mainly in the form of pressure differential (this is the explanation for why direct downwind version can exceed wind speed for a limited amount of time).

Offline electrodacusTopic starter

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Re: Newton's third law problem.
« Reply #171 on: November 27, 2022, 08:29:29 pm »
The formular for the drag power is the frist one, but this is the power theoretical possible to take from the wind and that is not the power needed for the vehicle to drive. The power for the vehicle is more like the 2nd formular.

It is obvious that the first formula can not be corrent for the power of the vehicle: if the vehicle changes direction from going against the wind to going with the wind it changes from needing power to drive to gaining power from the wind. So the sign in the power has to change at around 0 vehicle speed.
Another way is to look at the force need: mechnical power is force times speed, more or less by definition. The force from the wind is limited and approaching zero speed the power this also has the approach zero.

The relevant question for the vehicle is if the motor can provide sufficient force. The power only determines how fast the vehicle can go. With low speed very little power is sufficient.

I do not think that second formula describes anything. I'm fairly certain one or more people that do not understand what power is came up with that as they were likely thinking the correct one outputs a value larger than they expected or wishing.

Yes as you see the sign changes correctly when vehicle speed is zero.

Equation contains this (wind speed-vehicle speed)  so max wind power to accelerate the vehicle is proportional with (wind speed - 0)3
If vehicle drives downwind it can be powered by wind at (wind speed - vehicle speed)3
If vehicle wants to drive upwind it requires a power proportional with (wind speed - (-vehicle speed))3 same as saying (wind speed + vehicle speed)3
So is clear from this that no vehicle can exceed wind speed powered only by the wind and can not drive at any speed upwind.
And yes all this is correct. Any wind powered vehicle that exceeds wind speed will do so with either stored energy or another energy source other than the wind and same is true for a vehicle driving upwind at any speed.

When you think at a zero speed vehicle you are wrongly thinking about a vehicle anchored to the ground.  But that anchoring to ground just means vehicle is now part of earth.

Offline electrodacusTopic starter

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Re: Newton's third law problem.
« Reply #172 on: November 27, 2022, 08:38:18 pm »
You've scoured the internet to find 'examples' where someone has made an error somewhere that supports your argument, but those errors are painfully obvious with just a little bit of a fair-minded consideration.

In the Wolfram example, they clearly have only considered the case where the vehicle speed is the same as the speed of the fluid relative to the body, as in driving in still air.  That is obvious simply looking at the equations.

In your other example, if you bother to read their explanations elsewhere on their website under "Vehicle Physics" they say:

Now, the propulsion power can be calculated as a product of driving resistance and vehicle speed:

But from the operation of the malfunctioning calculator app, you can see that they have not incorporated this into their algorithm. 

In neither case do they use the equation you claim they do.

The Wolfram example has at least one part right before they go and screw it up.  P = FD * Vvehicle

It took me all of 3 or 4 minutes to find those two links.

You should read again to understand what that (the thing you highlighted) actually means.
A vehicle on frictionless wheels will be no different from a floating balloon.
Yes when friction is added that is subtracted from the wind power available to vehicle.

They properly incorporated the algorithm and that calculator outputs the correct results.
Look at what is defined as v in that equation as it is not the vehicle speed.
Quote from the text under that equation
"v is speed of the fluid relative to the body"
Which translates for this case in to v = (wind speed - vehicle speed)

Offline bdunham7

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Re: Newton's third law problem.
« Reply #173 on: November 27, 2022, 09:43:57 pm »
You should read again to understand what that (the thing you highlighted) actually means.
A vehicle on frictionless wheels will be no different from a floating balloon.

Both of those links purport to calculate the power needed to drive a vehicle against a fluid drag, not the other way around.
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

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Re: Newton's third law problem.
« Reply #174 on: November 27, 2022, 10:04:29 pm »
Both of those links purport to calculate the power needed to drive a vehicle against a fluid drag, not the other way around.

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.

You can just use negative sign in that calculator to calculate wind power available to accelerate so tailwind.


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