6 ms·

Haha, nice way to beat the system. But I doubt the symmetry of those two graphs. Surely, there is no (ordinary) retail car on the planet which can accelerate a

by drucken 15y ago

Haha, nice way to beat the system. But I doubt the symmetry of those two graphs. Surely, there is no (ordinary) retail car on the planet which can accelerate as fast as it decelerates?

ktizo 15y ago
I doubt there is any car that can unless the brakes are really dodgy (apart from the rocket powered ones with parachutes).. Just goes to show, if you haven't got a hope in hell, try bullshit and long words. [edit] Just looked up formula one cars, they are 2g acceleration and 5g braking apparently.
tedmiston 15y ago
First comment: "venky said... He claims in his model, 'his car decelerated at - 10 m/s^2 and, instantaneously, accelerated to + 10 m/s^2 at t = 0'. No known mechanical system is capable of achieving such an instantaneous jump without a tail-off period. ...."
- xxbondsxx 15y ago
  MechE here, electrical motors can obtain almost instantaneous acceleration / full torque at 0rpm. Their torque curves typically look like this: http://www.jmag-international.com/catalog/img/e68-3b.gif http://www.jmag-international.com/catalog/img/e68-3b.gif The brakes are independent, so it's not as if one system has to provide both accelerations, one just needs exceptional timing of the feet. A lot of rally car drivers can do similar maneuvers This is the same reason why the Tesla Roadster has such a killer 0-40mph
mistercow 15y ago
First, we assume a spherical car...
- RegEx 15y ago
  Ah, the perfect physics world. It's a fun place to go from time to time.
excuse-me 15y ago
A modern hatchback (VW Golf) with good tires on a perfect road can decelerate at 1g with a pro driver. In tests regular drivers posted between 0.9 - 0.6g in a range of cars from Ferrari to Honda civic. To do 1g in acceleration you would need to do 0-60 in 2.75s that MIGHT be possible for a $1M supercar (or a bike ;-)
- joshu 15y ago
  I think a GT-R can do that. It's certainly close.
  - rdl 15y ago
    GT-R is a $1mm supercar that happens to be underpriced at $80k.
    - joshu 15y ago
      Wut
    - reneherse 15y ago
      Which is what happens when the techniques of lean manufacturing are applied to the supercar design brief. First of this vein was the Honda NSX, I believe. I have a hunch that the reliability of these cars far exceeds that of the big Italian names...
      - joshu 15y ago
        I belong to a car club that lets you take these out. Supposedly the GT-R eventually disintegrates its own transmission. So did a Ferrari F430. The newer Ferraris don't anymore, supposedly.
        lmm 15y ago
        IIRC if you use the launch control that explicitly (as in documented in the manual) puts several hundred miles' worth of wear on it - and I'd guess anyone who takes it out in a car club like that will try it at least once (I know I would). Could it just be that?
loverobots 15y ago
But then the prosecution would have to bring it's own expert witness...over a traffic ticket.
xxbondsxx 15y ago
MechE here, the limiting factor for car accelerations is usually the static coefficient of friction between the car tires and the road, _not_ the power of the brakes or strength of the engine. Without ABS braking, it is quite easy to "skid" while applying a harsh brake because you overcome the limit of force between the tires and the road. Similarly, it is quite easy to "burnout" as well with a strong engine for the same reason. So although the strength of the two systems is not the same, the limiting factor for both of them is identical. Hence, symmetry.
- shasta 15y ago
  Car owner here. I don't think this is right.
  - kronusaturn 15y ago
    Yeah, this argument would only apply to all-wheel-drive cars that are powerful enough to burnout on all four wheels.
    - xxbondsxx 15y ago
      It actually applies in a few cases: * All wheel drive cars, with all-wheel braking * Two-wheel drive cars, with braking systems that are primarily biased towards the front. Both cases rely on either all four wheels or accel/decel or only two
- jsight 15y ago
  The limiting factor on acceleration in the Toyota Yaris is ont the tires.
- cellularmitosis 15y ago
  This is true for the deceleration side of things (nearly any car can lock it's brakes at any speed), but on the acceleration side of the curve, this is typically only true in first, and perhaps second gear. It would take a truly obscene amount of power to smoke the tires while already in 5th gear (assuming you dont "cheat" by popping the clutch).

by drucken 15y ago

Haha, nice way to beat the system. But I doubt the symmetry of those two graphs. Surely, there is no (ordinary) retail car on the planet which can accelerate as fast as it decelerates?

ktizo 15y ago

I doubt there is any car that can unless the brakes are really dodgy (apart from the rocket powered ones with parachutes).. Just goes to show, if you haven't got a hope in hell, try bullshit and long words. [edit] Just looked up formula one cars, they are 2g acceleration and 5g braking apparently.

tedmiston 15y ago

First comment: "venky said... He claims in his model, 'his car decelerated at - 10 m/s^2 and, instantaneously, accelerated to + 10 m/s^2 at t = 0'. No known mechanical system is capable of achieving such an instantaneous jump without a tail-off period. ...."

xxbondsxx 15y ago
MechE here, electrical motors can obtain almost instantaneous acceleration / full torque at 0rpm. Their torque curves typically look like this: http://www.jmag-international.com/catalog/img/e68-3b.gif http://www.jmag-international.com/catalog/img/e68-3b.gif The brakes are independent, so it's not as if one system has to provide both accelerations, one just needs exceptional timing of the feet. A lot of rally car drivers can do similar maneuvers This is the same reason why the Tesla Roadster has such a killer 0-40mph

mistercow 15y ago

First, we assume a spherical car...

RegEx 15y ago
Ah, the perfect physics world. It's a fun place to go from time to time.

excuse-me 15y ago

A modern hatchback (VW Golf) with good tires on a perfect road can decelerate at 1g with a pro driver. In tests regular drivers posted between 0.9 - 0.6g in a range of cars from Ferrari to Honda civic. To do 1g in acceleration you would need to do 0-60 in 2.75s that MIGHT be possible for a $1M supercar (or a bike ;-)

joshu 15y ago
I think a GT-R can do that. It's certainly close.
- rdl 15y ago
  GT-R is a $1mm supercar that happens to be underpriced at $80k.
  - joshu 15y ago
    Wut
  - reneherse 15y ago
    Which is what happens when the techniques of lean manufacturing are applied to the supercar design brief. First of this vein was the Honda NSX, I believe. I have a hunch that the reliability of these cars far exceeds that of the big Italian names...
    - joshu 15y ago
      I belong to a car club that lets you take these out. Supposedly the GT-R eventually disintegrates its own transmission. So did a Ferrari F430. The newer Ferraris don't anymore, supposedly.
      - lmm 15y ago
        IIRC if you use the launch control that explicitly (as in documented in the manual) puts several hundred miles' worth of wear on it - and I'd guess anyone who takes it out in a car club like that will try it at least once (I know I would). Could it just be that?

loverobots 15y ago

But then the prosecution would have to bring it's own expert witness...over a traffic ticket.

xxbondsxx 15y ago

MechE here, the limiting factor for car accelerations is usually the static coefficient of friction between the car tires and the road, _not_ the power of the brakes or strength of the engine. Without ABS braking, it is quite easy to "skid" while applying a harsh brake because you overcome the limit of force between the tires and the road. Similarly, it is quite easy to "burnout" as well with a strong engine for the same reason. So although the strength of the two systems is not the same, the limiting factor for both of them is identical. Hence, symmetry.

shasta 15y ago
Car owner here. I don't think this is right.
- kronusaturn 15y ago
  Yeah, this argument would only apply to all-wheel-drive cars that are powerful enough to burnout on all four wheels.
  - xxbondsxx 15y ago
    It actually applies in a few cases: * All wheel drive cars, with all-wheel braking * Two-wheel drive cars, with braking systems that are primarily biased towards the front. Both cases rely on either all four wheels or accel/decel or only two
jsight 15y ago
The limiting factor on acceleration in the Toyota Yaris is ont the tires.
cellularmitosis 15y ago
This is true for the deceleration side of things (nearly any car can lock it's brakes at any speed), but on the acceleration side of the curve, this is typically only true in first, and perhaps second gear. It would take a truly obscene amount of power to smoke the tires while already in 5th gear (assuming you dont "cheat" by popping the clutch).