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| Mess with your minds: A wind powered craft going faster than a tail wind speed. |
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| Brumby:
Let's revisit: --- Quote from: electrodacus on December 19, 2021, 05:45:16 am ---Do you understand that power you take from the wheel will brake the vehicle ? --- End quote --- I presume you mean energy. I certainly do - and the fact you want to make a point of this seems to be a desperate move to discredit me. Do you realise that while that extraction of energy will slow the vehicle, that the loss of velocity will result in the wind directly applying more force to the vehicle as it will be travelling below wind speed? This results in an increase in total power applied to the vehicle. Pull 5.5W from the wheels and, as the vehicle slows, the wind adds more power and, thus, more energy. Even if that additional power is just 2W or 1W or even 1mW, the overall energy delivered to the vehicle by the wind has increased. The above is perfectly reasonable and reads pretty clearly, even before throwing in the word "energy". There is no conflict in using the terms power or energy. Each describes a particular quantity and those terms can be mixed quite happily. It is for the reader to understand what information each quantity provides. The only difference is time and the context gives enough structure for the appropriate consideration of time. |
| electrodacus:
--- Quote from: Brumby on December 20, 2021, 08:07:40 am ---Let's revisit: --- Quote from: electrodacus on December 19, 2021, 05:45:16 am ---Do you understand that power you take from the wheel will brake the vehicle ? --- End quote --- I presume you mean energy. I certainly do - and the fact you want to make a point of this seems to be a desperate move to discredit me. Do you realise that while that extraction of energy will slow the vehicle, that the loss of velocity will result in the wind directly applying more force to the vehicle as it will be travelling below wind speed? This results in an increase in total power applied to the vehicle. Pull 5.5W from the wheels and, as the vehicle slows, the wind adds more power and, thus, more energy. Even if that additional power is just 2W or 1W or even 1mW, the overall energy delivered to the vehicle by the wind has increased. The above is perfectly reasonable and reads pretty clearly, even before throwing in the word "energy". There is no conflict in using the terms power or energy. Each describes a particular quantity and those terms can be mixed quite happily. It is for the reader to understand what information each quantity provides. The only difference is time and the context gives enough structure for the appropriate consideration of time. --- End quote --- I do not want to discredit you I'm just pointing the fact that you do not know what power is and also do not know the difference between power and energy. Yes taking power from the wheel will mean braking the vehicle but if you do not mention the amount of time you took the power then you have no idea how much the vehicle has slowed down. If you mention a time period say 1ns, 1ms or 1s then you also mentioned the amount of energy you extracted meaning you can calculate exactly by how much the vehicle slowed down. If you just mention power then you look at power input (what you take from the wheel) and the output power the one that propeller will output and if the output is equal or lower that the input (the only way it can be) then there is no acceleration. This example I used in my video uses power to calculate if there is a net power meaning acceleration or if that value is negative deceleration. Keep in mind this is the equivalent vehicle with wheels only so there is no air involved and no possibility to store energy in pressure differential. Also keep in mind that there is also no energy storage consider in the internal mechanism so no option to store energy inside the vehicle like it is the case with direct down wind version's including the toy vehicle with rubber band I showed in the video. Below are the correct equations and shows that if there is no energy storage available that will be the result. |
| IanB:
--- Quote from: electrodacus on December 20, 2021, 06:17:48 pm ---Below are the correct equations --- End quote --- If you would stop making assertions like this, and instead ask questions like, "Are these the correct equations?" or "What is the correct way to analyze this system?", then you would become far more enlightened. As it is, you are unable to make any progress in your understanding. |
| electrodacus:
--- Quote from: IanB on December 20, 2021, 06:32:03 pm --- --- Quote from: electrodacus on December 20, 2021, 06:17:48 pm ---Below are the correct equations --- End quote --- If you would stop making assertions like this, and instead ask questions like, "Are these the correct equations?" or "What is the correct way to analyze this system?", then you would become far more enlightened. As it is, you are unable to make any progress in your understanding. --- End quote --- If you disagree post what you think are the correct ones. I do not make a video without checking multiple times and making sure what I say is correct. I can of course still make mistakes as anyone else. Looking forward to your results for that problem. |
| Kleinstein:
The case with the wheels is a bit different from the prop case, but I think it contains the same difficulty in understanding. As an advantage the basics of mechanics are a bit simpler and less of an approximation. So it may be OK to look again at this simpler picture for the start. To judge if the equations are correct or not the first thing is to make clear what is meant with P_out and P_net mean and the condition for the vehicle. For the condition of the vehicle the situation to look at, the most useful case would be the vehicle standing still in the picture and with F_G = F_M to have a stationary case with no acceleration. So what do P_out and P_net stand for ? |
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