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Electroboom: How Right IS Veritasium?! Don't Electrons Push Each Other??
electrodacus:
--- Quote from: gnuarm on July 11, 2022, 06:25:01 pm ---
No, as is shown in this example, the same leverage is gained by a mechanism that pushes the sail toward the wind on the car. That's what tacking is doing, providing leverage to allow a vehicle to travel into the wind. No tacking is needed nor is helpful in traveling down wind. Using a fixed sail, a vehicle can not travel down wind faster than the wind. Install a moving sail or a propeller, and you can travel down wind.
You are a troll. You are a blatant, obvious troll. You will never admit to understanding what is going on here. The only reason you are posting is to get people to respond to you.
I should stop feeding the troll.
--- End quote ---
Need to correct my example as it was wrong. If sail moves at 2.5m/s relative to the ground when it is above it will move at 17.5m/s when under so the average is 10m/s
Tacking will not be considered direct down wind and had nothing to do with your example or direct down wind blackbird.
When traveling at an angle to wind direction vehicle speed with low enough friction will exceed wind speed.
What happens in that case is that vehicle kinetic energy will be the energy storage device and in ideal case with no friction all you need to do is exceed wind speed at an angle to wind direction then turn directly downwind and maintain that high speed as there is no friction to slow you down.
In real world where there is friction you will need to travel in zig-zag (Tacking) witch is not direct down wind as you still use energy storage but in this case you can take advantage of the existing kinetic energy of the vehicle and used that to store energy.
Naej:
--- Quote from: electrodacus on July 11, 2022, 04:50:44 pm ---
--- 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%)
--- End quote ---
Where is your proof that the quantity you called efficiency can never be more than 100% ?
electrodacus:
--- Quote from: Naej on July 11, 2022, 07:15:44 pm ---
Where is your proof that the quantity you called efficiency can never be more than 100% ?
--- End quote ---
First law of thermodynamics is something like this: Energy can be changed from one form to another, but it cannot be created or destroyed
This law also called the conservation of energy will not allow any system to be more than 100% efficient and it was never, ever demonstrated to be false thus the reason it is a law and not just a theory.
I will say at least as far as I'm concerned is the most important thing to understand in physics.
Naej:
--- Quote from: electrodacus on July 11, 2022, 07:23:17 pm ---
--- Quote from: Naej on July 11, 2022, 07:15:44 pm ---
Where is your proof that the quantity you called efficiency can never be more than 100% ?
--- End quote ---
First law of thermodynamics is something like this: Energy can be changed from one form to another, but it cannot be created or destroyed
This law also called the conservation of energy will not allow any system to be more than 100% efficient and it was never, ever demonstrated to be false thus the reason it is a law and not just a theory.
I will say at least as far as I'm concerned is the most important thing to understand in physics.
--- End quote ---
It's a good start, but on which isolated system are you applying it?
Why with 100W brought by gears and 1000W in wind, I can't get 300W in propulsion?
PlainName:
--- Quote from: electrodacus ---But you claim the vehicle will always accelerate (increase speed)
--- End quote ---
Wrong.
The equation I posted shows there is an upper limit to speed, and even without that I have never suggested it would accelerate perpetually or even at all in every case. In fact, I have expressly stated the opposite.
--- Quote ---The equation that I use predict exactly what happens.
--- End quote ---
Wrong.
--- Quote ---Best case you are describing a vehicle driving perpendicular to wind direction not direct down wind.
--- End quote ---
Wrong.
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