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Electroboom: How Right IS Veritasium?! Don't Electrons Push Each Other??
electrodacus:
--- Quote from: Naej on July 11, 2022, 08:43:33 am ---Yes. Excellent example. The energy storage you're searching for is: the wheels, the gears, the propeller blades and the vehicle.
--- End quote ---
Yes they are all energy storage devices but none of them allow exceeding wind speed in the way they are connected to vehicle.
You can with blackbird as it is exceed wind speed in theory without storing pressure differential energy storage while below wind speed.
They were allowed to have variable pitch propeller (why not as the judges had no idea what energy storage is).
So imagine a blackbird set with propeller blades at zero so no propulsion due to propeller and no energy storage.
The propeller will be geared to spin very fast so part of the wind energy will be stored as rotational kinetic energy (basically a flywheel) then this ideal vehicle can get to wind speed but not faster and this is where the pilot starts to change the propeller pitch converting the flywheel stored energy in to vehicle kinetic energy thus increasing for a bit the speed of the vehicle above wind speed.
But this is a different method of accelerating the vehicle above wind speed using stored kinetic energy in flywheel and not stored pressure differential.
gnuarm:
--- Quote from: electrodacus on July 11, 2022, 04:16:03 pm ---
--- Quote from: gnuarm on July 11, 2022, 06:21:44 am ---
You aren't understanding. The sails move at a quarter the rate of the vehicle. So when the vehicle is moving at twice the speed of the wind, the wind is still hitting the sails at one half the wind speed relative to the ground.
Uh, no, the sails move from the front of the vehicle to the rear in a straight line along a belt. The sails collapse on reaching the rear, so they can follow the belt under the vehicle and be pulled back up on reaching the front of the car. I created this model. If you don't understand, I suggest you create an animation to help you visualize it.
You literally can't understand this can you? The only speed of the sail that matters, is the speed when it is catching the wind. At that time it is moving wrt to the ground slower than the wind, so receives power from the wind, while the car is moving forward, faster than the wind.
Please create the animation. But if you think the velocity of the sail when it is folded up has anything to do with the problem, there is nothing anyone can say to you to help you understand, or.... you do understand, but you are not capable of acknowledging you have been wrong all this time. Even money, either way.
--- End quote ---
I can create an animation in my head and since I know the physics involved it will be consistent with reality.
--- End quote ---
You clearly are failing to understand the physics.
--- Quote ---The sail move at a quarter of the vehicle speed when it is above the vehicle and at one and a quarter the vehicle speed when bellow the vehicle with average sail speed being exactly the speed of the vehicle.
That is what it means to move around the vehicle.
Since no balls can hit any part of the vehicle including the sail when their average speed is equal the vehicle kinetic energy can not increase thus speed can not increase.
--- End quote ---
You just failed both your physics test and your math test.
No sail is moving at the "average" speed, so that is completely irrelevant. The wind will impact the sail when it is moving at half the speed of the wind. When it is moving at any other speed, it is furled up and not impacted by the wind.
You literally do not understand physics... or more likely, you understand perfectly, but like playing your troll game.
--- Quote ---
--- Quote ---Blah, blah, blah. The sail does not exceed the speed of the wind, so the equation applies perfectly.
--- End quote ---
On blackbird the sail exceeds wind speed when vehicle exceeds the wind speed as they do have the exactly same speed.
--- End quote ---
This is not a blackbird where you don't understand the physics. This is a different mechanism where you don't understand the physics.
--- Quote ---
--- Quote ---Blah, blah, blah... you can't squirm your way out of this with your nonsense. None of that applies to a sail boat. This is just a sail boat geared to the car. Wind on sail, moving the car faster than the wind, while the sail moves slower than the wind. There is no energy storage bunkum like you want to apply to the Blackbird.
--- End quote ---
No sail boat or sail vehicle can exceed wind speed directly downwind.
--- End quote ---
Any yet, they do, as proven by the multiple videos.
You have entered another realm of denial. I'm not going to continue to listen to your BS. I'm convinced that no one who claims to understand physics would not understand this simple model. So you must be trolling.
electrodacus:
--- Quote from: Naej on July 11, 2022, 08:48:46 am ---
Again, I defined the word YOU used so you should know.
The propeller applies the force on the car, car speed relative to ground, and mechanical power on input is what comes from the wheels (by gears).
What you said is correct in still air, and completely incorrect when there's a wind.
Of course you didn't prove what you said so you shouldn't be surprised it's completely incorrect.
If you prefer, you take my example above where the propeller takes 1000W of wind power, and puts 300W in the car so it's "30% efficient" (for a different definition of efficiency, obviously).
--- End quote ---
Thanks for clarifying the definition.
Say we are at wind speed so the force applied by propeller is the only one as air particle have same speed thus wind speed relative to vehicle is zero.
We start with input and say that vehicle speed and wind speed are equal at 10m/s
Vehicle takes at the wheels 100W that means a braking force of 100W/10m/s = 10N
Take this 100W and apply to propeller witch is say 70% efficient (ideal case will be 100% obviously never, ever more than 100%)
So the force that propeller will apply will be ( 100W / 10m/s ) * 0.7 = 7N
Since braking force is higher than propulsion force the vehicle will slow down.
When vehicle is below wind speed it will be helped by wind but once at wind speed and above wind power is no longer able to help the vehicle increase kinetic energy but on the contrary it will start to hinder that.
electrodacus:
--- Quote from: imo on July 11, 2022, 09:30:19 am ---
--- Quote ---The world land speed record for a wind-powered vehicle was broken on 26 March 2009 by Briton Richard Jenkins in his yacht Greenbird with a speed of 126.1 mph (202.9 km/h). Wind speeds were fluctuating between 30–50 mph (48–80 km/h) at that time.
--- End quote ---
https://www.wikiwand.com/en/Land_sailing
--- End quote ---
Do you understand that we are discussing the special case of direct downwind ?
A sail vehicle traveling at an angle to wind with best case perpendicular to wind direction can exceed wind speed and maintain that indefinitely as wind speed relative to vehicle is not zero.
With direct down wind as soon as vehicle speed equals wind speed the wind speed relative to vehicle will be zero and thus no wind power available to vehicle.
electrodacus:
--- Quote from: dunkemhigh on July 11, 2022, 10:51:39 am ---
--- Quote from: gnuarm ---I'm not sure, but I think ED is playing dumb so he doesn't have to deal with the reality of this car which clearly can move down wind faster than the wind. He will insist on changing the case and turn it into something where he can obfuscate and confuse the facts.
--- End quote ---
Exactly that. It would be the prefect definition of trolling technique were it not that he believes what he's posting.
--- End quote ---
I promise I believe what I post. And believe is not even the right word since I know that is the case (it is how the universe works).
The equation that I use predict exactly what happens.
What you claim is not what happens. As blackbird or the treadmill vehicle are both reducing the acceleration rate as stored energy is used up and they will decelerate as soon as all that stored energy is used up.
But you claim the vehicle will always accelerate (increase speed) witch is inconsistent with energy conservation.
Best case you are describing a vehicle driving perpendicular to wind direction not direct down wind.
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