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| Electroboom: How Right IS Veritasium?! Don't Electrons Push Each Other?? |
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| electrodacus:
--- Quote from: Naej on July 13, 2022, 01:00:12 am ---What you don't realize is that there's a ton of energy in the ball moving at 10m/s, so energy can be conserved even if the car accelerates. You just have no grasp on the concept of momentum, which is why you can't compute the recoil on the bat. And it's ok, but you have to believe people who do, and they tell you: the bat recoil gives more energy to the car than what it took from the wheel. Energy is conserved but you must not forget energy outside the car or else you say wrong things. --- End quote --- I told you exactly how much energy is in that ball 50000Ws I also told you how much was taken from it and delivered to the vehicle and that was ideal case 2Ws So what are you asking exactly ? You just do not get what energy is. Momentum is useless when you already know the kinetic energy. momentum is m*v while kinetic energy is 0.5 * m * v2 You can get the speed of the ball and the vehicle both from momentum and from kinetic energy. The result will not be different. |
| PlainName:
--- Quote from: electrodacus ---No I do not agree. At no point the propeller on direct downwind blackbird is producing thrust. If propeller was say connected to an electric motor and a battery then yes propeller will produce trust. --- End quote --- Really? Seriously? The propeller has knowledge of its power source? Either you're using the wrong words (to match your wrong equation) or their real meaning has escaped you. |
| PlainName:
--- Quote ---I have not learned why it is that people, who also have learned what I've learned about this discussion style, are still willing to continue to discuss the issue. --- End quote --- Perhaps because we are not so much different - whether you have the right or wrong idea, are clever or stupid, the Internet has to be corrected :) |
| Naej:
--- Quote from: electrodacus on July 13, 2022, 01:17:38 am ---Momentum is useless when you already know the kinetic energy. --- End quote --- Clearly you never learned physics. It's ok but stop believing you're the best, and that what you say must be true just because you wrote it, or you'll never learn anything with this kind of attitude. Alright so here's how it works. I replaced the 1t balls by walls, and this is how the car is propelled: a ball (elastically) bounces on the wall, then on the car, then it is accelerated back towards the wall. Speeds in ground reference frame: - wall : 10m/s - car : 20m/s - ball : -10m/s Using 50J for the ball, you get a mass of 1kg. Because 1kg<<1t, you get a collision like on a wall. So in the reference frame of the ball, the speed of the bat is (approximately) its opposite. It is -10-10=-20 m/s and turns into 20m/s, which in the ground reference frame is 30 m/s. Because 1kg<< the mass of the car, you also get a collision like on a wall. In the reference frame of the car, the speed of the ball is 30-20=10 m/s, so the reflected ball is at -10 m/s, which in the ground reference frame is 10 m/s. You need to remove 20 m/s to restart the cycle, so you take the energy for it at the wheel. In the reference frame of the car, the speed must go from -10 m/s to -30m/s so you need 1/2*1kg*(30²-10²)=400J to accelerate the ball. The momentum gained is m*delta v=m*(30-(-30))=60 kgm/s, which means you can add delta p*car speed=1200 J to the car kinetic energy in the ground reference frame. You remove the 400J taken at the wheel and you just added +800J to the car. Repeat until reaching the desired speed. Now if you don't believe this: 1) make sure you really understand momentum, reference frames, energy (there are high school physics books out there) 2) tell me where I'm wrong 3) don't talk about supercapacitors |
| electrodacus:
--- Quote from: dunkemhigh on July 13, 2022, 08:49:24 am ---Really? Seriously? The propeller has knowledge of its power source? Either you're using the wrong words (to match your wrong equation) or their real meaning has escaped you. --- End quote --- What is the only way moving air particles (wind) interact with the vehicle ? Since for direct downwind version of blackbird air particles are the only thing driving the vehicle even after vehicle exceeds wind speed (because the way energy is stored is by creating a pressure differential) there is no time where propeller has propulsion role just role of sail and help with energy storage. It is like you saying that a sail pushes the air particles and not the other way around. So when a air particle or a 1.2kg ball hits the propeller blade that is all the propulsion that vehicle will see. While in motion both propeller and air particle or ball move but since all the energy to accelerate the vehicle comes from air molecule or 1.2kg ball the net interaction between propeller blade witch rotates in tandem with vehicle speed as it is connected through a fixed gear to wheels will be provided by the air/wind and not propeller which is actually powered by wind. Propeller will not know that it exceeded wind speed since as long as propeller is concerned it is still being hit by air particles due to pressure differential stored energy. The air particle / 1.2kg ball analogy always hits with more energy than it is hit back by the propeller that is why the vehicle accelerates as vehicle uses that excess to increase the kinetic energy and thus speed. |
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