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Electroboom: How Right IS Veritasium?! Don't Electrons Push Each Other??
Naej:
--- Quote from: electrodacus on July 11, 2022, 03:01:51 am ---Maybe as this is an electrical forum people here have a bit better intuition about electricity (possibly just wishful thinking on my part).
Input is a CV-CC lab power supply rated at 200W 20V and 10A max
Say you want 30V. Is it possible to add a circuit between the output of the 200W lab power supply that has no energy storage device and get 30V on the other side?
What about 15A ? What about more than 200W for some limited amount of time?
Is any of that possible without having a energy storage device in that circuit ?
--- End quote ---
Yes. Excellent example. The energy storage you're searching for is: the wheels, the gears, the propeller blades and the vehicle.
Naej:
--- Quote from: electrodacus on July 11, 2022, 12:32:58 am ---
--- Quote from: Naej on July 11, 2022, 12:19:10 am ---Did you read the first part?
It says: Let's say efficiency is defined as force*car speed/mechanical power on input so that your argument works.
So it's not efficiency with respect to wind power.
If you have 1000W in wind energy you can for example leave 700W in the air, use 100W for the drag of the vehicle, 100W to compensate tire friction, 100W for accelerating.
So the propeller gets 300W out of 100W in mechanical input, or 300% efficiency.
Note that I used a definition of efficiency to match your use of the word.
--- End quote ---
Please define exactly the "force*car speed/mechanical power on input"
What applies that force ?
car speed relative to ground or wind?
and what is exactly mechanical power on input?
--- End quote ---
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).
--- Quote from: electrodacus on July 11, 2022, 12:32:58 am ---If mechanical input to a propeller is 100W the output will be in ideal case 100W and in real world more like 70W for an efficient propeller in air.
--- End quote ---
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).
iMo:
--- 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
PlainName:
--- 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.
electrodacus:
--- 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.
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.
--- 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.
--- 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.
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