I'll guess that you never passed any fluid mechanics courses either.
See? I can return snark for snark. Now let's actually discuss some physics.
There's a fundamental difference between applying thermodynamics in this case, and the regenerative braking one. That you don't know that is what's damning.
For the same trip from New York to Boston in a Toyota Camry, traveling at 80 mph the whole way takes 2.75 times as much energy as traveling at 30 mph. See http://ocw.mit.edu/courses/physics/8-21-the-physics-of-energ... and apply scaling factors to verify.
That provides a lot of headroom to add starts and stops on the 30 mph trip without using more energy than the faster trip. In fact, even without regenerative braking, you could add in multiple stops/starts per mile and the slow trip still saves energy in a conventional car. (Well, until you consider rolling friction going up hills, I don't have a good back of the envelope for what that adds.)
I'm being deliberately unfair to make a point here. Standard "highway driving" for EPA efficiency is assumed to be 60 mph. Traveling at 80 mph is a lot, lot worse than 60 mph. Elon knows this, and calls out the journalist's speed because Elon knows what difference this efficiency makes.
If the highway trip is taken at 60 mph it is much harder for a slow trip to take less energy.
Now do you understand that speed hurts efficiency?
> See? I can return snark for snark. Now let's actually discuss some physics.
Not snark. Also, already knew about the possible non-intuitive results with water.
> If the highway trip is taken at 60 mph it is much harder for a slow trip to take less energy.
Now do you understand that speed hurts efficiency?
Hmmm, putting words in my mouth to spin it so it seems like my original position is actually yours and imply that I don't know a different basic bit of physics. (You can check my recent comment history.)
Nope, definitely wouldn't hire you as a journalist.
Go back to http://news.ycombinator.com/item?id=5218597 and look at the quote you were criticizing Broder for. Here it is. Based on that advice, I was under the impression that stop-and-go driving at low speeds in the city would help, not hurt, my mileage.
You considered this proof that he didn't know basic physics, because obviously stop-and-go driving is inefficient. My point is that your criticism is wrong because this is actually a question of empirical fact that can - and does - go either way. (In fact in published mpg figures, the Toyota Prius does better in stop and go city traffic than on the highway. If you go significantly over 55 mph on the highway, you're probably getting worse highway mileage than the published figures.)
...imply that I don't know a different basic bit of physics.
I make no claims on whether you understand how wind resistance works. I do claim that your initial comment showed no understanding for how important wind resistance is IN THIS CASE. But now I pointed it out, and then explained it with reference to actual energy loss for a popular model of car, and you have been pointed to the fact that published mpg figures for the Prius demonstrate that it leads to the very pattern that you thought Broder was an idiot for thinking possible. At this point if you believe in science and measurement, you've got to admit that your analysis missed something important, and you were wrong. If you're a mature person, you'd then apologize for some of the same things.
Alternately you can demonstrate a willful denial of basic physics by continuing to insult me for having pointed out your mistake. But if you continue that path, I won't bother to respond because I trust that interested third parties can draw the correct conclusion.
And then, you proceed to talk about an entirely different set of comments. Perhaps we've been misunderstanding referents. In my reading, it seems like you've been painting me as a rube who might think that warmer water freezing faster than cold is impossible. I find that highly annoying, because that's false.
I see your point about slower driving, regen, and range. Imagine you're the manager of a group of delivery truck drivers, and a driver comes to you after having stranded himself on a trip, and gives you that same sentence. Most people are going to look at him like he's an idiot, or have to try not to. Even knowing how regen braking works, I would still probably give him that look.
> If you're a mature person, you'd then apologize for some of the same things.
I'll apologize. The motivation for my objection was to how you seemed to be trying to paint my knowledge. From my reading, you were willfully trying to paint a picture of my knowledge or lack of it. From you POV, you were trying to make a point about the capabilities of regen braking, and saw my continued objection as a denial of that, which misconstrues of my position. (Heh, you could get the referents wrong on that last sentence too, prolonging this as well, hopefully not.)
Thank you for starting to apologize. You said a lot more that I'd appreciate apologies, but it is a good start.
Now it is my turn.
You're right that I said that you probably didn't know about the hot/cold water freezing weirdness when I had no evidence of that. I shouldn't have assumed ignorance as strongly as I did, and I apologize for having done so. A large part of the reason that I did is irritation with you for saying that anyone who could think that slow stop and go could possibly be more efficient than highway driving is an idiot who doesn't know basic physics. Since I consider that possible, and I think I know basic physics, this hit a nerve.
The reason why I brought up the water example is the following parallel. We have a situation where an obvious fact leads anyone with a basic physics education to assume that the answer goes one way. In fact it lead a lot of scientists to assume that they knew the answer, despite widespread folk knowledge and historical observations to the contrary. In fact reality is more complicated, and the obvious answer in this case isn't always right.
Now are you willing to admit that he and I weren't necessarily ignorant of basic physics when we say that slow stop and go can possibly be more efficient than highway traffic? And that furthermore the fact that I would say so is not particularly damning about my knowledge base or intelligence?
Imagine you're the manager of a group of delivery truck drivers, and a driver comes to you after having stranded himself on a trip, and gives you that same sentence. Most people are going to look at him like he's an idiot, or have to try not to.
You may not be giving truck drivers enough credit. Truck drivers make their living trying to beat operational costs while driving something with the aerodynamics of a brick. I have a couple of relatives who have been long-distance truck drivers, and they are keenly aware of the value of driving slowly, drafting off of other trucks, making no unnecessary maneuvers, etc.
> Thank you for starting to apologize...it is a good start.
It would help if you understood my position.
> I shouldn't have assumed ignorance as strongly as I did, and I apologize for having done so.
That's a good start.
> A large part of the reason that I did is irritation with you for saying that anyone who could think that slow stop and go could possibly be more efficient than highway driving is an idiot who doesn't know basic physics.
No, what I'm saying is that (despite the fact that someone who knows basic physics could figure out that it could possibly be more efficient) someone who knows basic physics who goes and makes a bet against being stranded without more info than Broder had is an idiot or is willfully acting like one.
> You may not be giving truck drivers enough credit. Truck drivers make their living trying to beat operational costs while driving something with the aerodynamics of a brick. I have a couple of relatives who have been long-distance truck drivers, and they are keenly aware of the value of driving slowly, drafting off of other trucks, making no unnecessary maneuvers, etc.
Wow, you really don't do it on purpose, do you? Feel free to read my sentence from the POV that truck drivers are very good at what they do.
I've never disputed that the "journalist" had a clear axe to grind. I've just disputed your claim about the sheer stupidity of that particular statement.
And about truck drivers, I did read your sentence from the POV that truck drivers are very good at what they do. Which is why I disagreed with you about how they would react.
I'll guess that you never passed any fluid mechanics courses either.
See? I can return snark for snark. Now let's actually discuss some physics.
There's a fundamental difference between applying thermodynamics in this case, and the regenerative braking one. That you don't know that is what's damning.
For the same trip from New York to Boston in a Toyota Camry, traveling at 80 mph the whole way takes 2.75 times as much energy as traveling at 30 mph. See http://ocw.mit.edu/courses/physics/8-21-the-physics-of-energ... and apply scaling factors to verify.
That provides a lot of headroom to add starts and stops on the 30 mph trip without using more energy than the faster trip. In fact, even without regenerative braking, you could add in multiple stops/starts per mile and the slow trip still saves energy in a conventional car. (Well, until you consider rolling friction going up hills, I don't have a good back of the envelope for what that adds.)
I'm being deliberately unfair to make a point here. Standard "highway driving" for EPA efficiency is assumed to be 60 mph. Traveling at 80 mph is a lot, lot worse than 60 mph. Elon knows this, and calls out the journalist's speed because Elon knows what difference this efficiency makes.
If the highway trip is taken at 60 mph it is much harder for a slow trip to take less energy.
Now do you understand that speed hurts efficiency?