Physics Blogging Round-Up: Fast Cars and Spherical Cows [Uncertain Principles]

It’s been a while since the last Forbes links dump, but since it’s the last day of the month, I figure I might as well sum up a bit. Only two posts, but they have a connection that I’ll expound on a bit to make up for the lack of material…

— Can A Tesla Model S Really Accelerate Faster Than Gravity?: I got pointed to a story about the 0-60mph time for a Tesla, and said “That seems fishy…” After climbing back out of the Google rabbit hole, I tried to explain why that seemed unlikely to me, and the funny timing thing that might explain the result.

— The Hardest Thing To Grasp In Physics? Thinking Like A Physicist: Some musings about how the trickiest part of learning to be a physicist is getting the mindset, particularly the highly reductionist use of “spherical cow” sorts of approximations.

So, the first of these really pissed off a lot of Car Guys, who left tons of comments, and some angry emails and tweets, pointing to a variety of other cars that supposedly accelerate at large multiples of the acceleration of gravity. I wasn’t especially moved by most of this, in part because they’re not particularly relevant to the question of whether the Tesla result is surprising. It’s true that I didn’t discuss the possibility of aerodynamic down forces that would allow for a larger frictional force, but those aren’t actually important for a normal-ish car like a Tesla. A top fuel dragster is a completely different animal, and I’m not especially surprised that they work differently than an ordinary car.

The other issue I have with the angry reaction is that it really misses the point of the post (which, admittedly, I probably should’ve made more explicit). That is, I don’t actually care whether the Tesla accelerates at 0.98g or 1.1g. My purpose in writing that piece, like most of what I write, really had more to do with the physics mindset than the specific numerical values. I was explaining my reaction and reasoning: when I read the original piece, I was immediately skeptical for reasons that have to do with physics, which sent me off looking for more information that might explain the faster-than-expected time in a way that didn’t require surprising physics, and learned about a timing thing that’s in the right ballpark to account for the apparent discrepancy.

I thought that was an interesting process (obviously, or I wouldn’t’ve been sucked into Googling stuff about car testing), and worth laying out. I’m really not remotely invested in the specific numerical results– if the tires they use turn out to be much stickier than the usual run of things so the acceleration is a little higher than I would expect, well, that’s a nice bit of trivia. It doesn’t really change my thinking about why that was a piece worth writing, which is largely that it illustrates the toy-model-building described in the second post. Thinking like a physicist means that the 0-60mph time isn’t just a random factoid that could take on absolutely any value, it’s something with a physical origin that you can model in a simple way, which leads to an expectation about what the time should be for a relatively ordinary car. And thinking “that’s funny…” does, in fact, lead to something that’s a little funny in the timing, which is also interesting.

But, yeah, I should’ve made that clearer, because, wow, are there people who are deeply invested in the accuracy of those numbers…

Anyway, that’s the story of my recent blogging. Which may become sparse for the next several months, as I’ve gotten myself stuck on a grand jury that sits two days a week, and classes start next Wednesday, so my time is going to be very tight for the immediate future.

from ScienceBlogs http://ift.tt/2bR9vMS

It’s been a while since the last Forbes links dump, but since it’s the last day of the month, I figure I might as well sum up a bit. Only two posts, but they have a connection that I’ll expound on a bit to make up for the lack of material…

— Can A Tesla Model S Really Accelerate Faster Than Gravity?: I got pointed to a story about the 0-60mph time for a Tesla, and said “That seems fishy…” After climbing back out of the Google rabbit hole, I tried to explain why that seemed unlikely to me, and the funny timing thing that might explain the result.

— The Hardest Thing To Grasp In Physics? Thinking Like A Physicist: Some musings about how the trickiest part of learning to be a physicist is getting the mindset, particularly the highly reductionist use of “spherical cow” sorts of approximations.

So, the first of these really pissed off a lot of Car Guys, who left tons of comments, and some angry emails and tweets, pointing to a variety of other cars that supposedly accelerate at large multiples of the acceleration of gravity. I wasn’t especially moved by most of this, in part because they’re not particularly relevant to the question of whether the Tesla result is surprising. It’s true that I didn’t discuss the possibility of aerodynamic down forces that would allow for a larger frictional force, but those aren’t actually important for a normal-ish car like a Tesla. A top fuel dragster is a completely different animal, and I’m not especially surprised that they work differently than an ordinary car.

The other issue I have with the angry reaction is that it really misses the point of the post (which, admittedly, I probably should’ve made more explicit). That is, I don’t actually care whether the Tesla accelerates at 0.98g or 1.1g. My purpose in writing that piece, like most of what I write, really had more to do with the physics mindset than the specific numerical values. I was explaining my reaction and reasoning: when I read the original piece, I was immediately skeptical for reasons that have to do with physics, which sent me off looking for more information that might explain the faster-than-expected time in a way that didn’t require surprising physics, and learned about a timing thing that’s in the right ballpark to account for the apparent discrepancy.

I thought that was an interesting process (obviously, or I wouldn’t’ve been sucked into Googling stuff about car testing), and worth laying out. I’m really not remotely invested in the specific numerical results– if the tires they use turn out to be much stickier than the usual run of things so the acceleration is a little higher than I would expect, well, that’s a nice bit of trivia. It doesn’t really change my thinking about why that was a piece worth writing, which is largely that it illustrates the toy-model-building described in the second post. Thinking like a physicist means that the 0-60mph time isn’t just a random factoid that could take on absolutely any value, it’s something with a physical origin that you can model in a simple way, which leads to an expectation about what the time should be for a relatively ordinary car. And thinking “that’s funny…” does, in fact, lead to something that’s a little funny in the timing, which is also interesting.

But, yeah, I should’ve made that clearer, because, wow, are there people who are deeply invested in the accuracy of those numbers…

Anyway, that’s the story of my recent blogging. Which may become sparse for the next several months, as I’ve gotten myself stuck on a grand jury that sits two days a week, and classes start next Wednesday, so my time is going to be very tight for the immediate future.

from ScienceBlogs http://ift.tt/2bR9vMS