6 ms·

Automatically != instantaneously. You'd have to make sure the car is far away enough that speed(car)^2/distance(you, car) < friction(rubber, pavement)*g. You c

Automatically != instantaneously. You'd have to make sure the car is far away enough that speed(car)^2/distance(you, car) < friction(rubber, pavement)*g. You can't play blindfolded frogger. EDIT: "friction" is a better function name than "mu", even though we all feel nostalgic for high school physics.

NovaS1X 12y ago
Yep! Latency and Inertia still exist with autocars. Anyone wishing to challenge physics may as well be awarded a Darwin Award.
Cakez0r 12y ago
I can't possibly work that out. The only answer is self-driving segways!
happyscrappy 12y ago
There is a table saw that stops the blade the instant it senses the capacitance of a finger. It completely ruins the saw but saves the finger. Something like that could work here if the car could see the pedestrian far enough in advance to stay within parameters. Ruins the road and the car not the pedestrian.
- darkmighty 12y ago
  If you stop the car instantly that's equivalent to a crash for the car occupants.
  - afarrell 12y ago
    It is in fact a pretty jerkish thing to do.
- jccooper 12y ago
  Those jam an aluminum block into the blade. I'm not sure what the equivalent would be for a car. Perhaps you could line the bottom of the car with rubber and then blow the wheels off. But there's plenty of problems with varying road surface and conditions and having a system that's never used. But a decent brake system and tires can do 1G, which is pretty good. I suppose you could go to maybe 5G for a true emergency brake system (which would be pretty rough on the occupants, eyeballs-out), but it hardly seems worth the cost (in money, weight, maintenance, accidental triggering, etc.) compared to good sensors and the existing braking systems.
  - pluma 12y ago
    I think the equivalent of jamming a block of solid aluminium into a spinning blade would involve some kind of anchoring. It would ruin the car and likely damage the road but as long as the passengers can be protected from the rapid deceleration, it just might save a life. OTOH you could just wrap the entire car in airbags and protect pedestrians the same way you protect the passengers. Not sure how practical or useful that would be, though.
  - joncrocks 12y ago
    Yeah, and don't forget that the car has people in it too :-) While you can instantaneously stop a saw blade to save a finger, stopping a car 'quickly' will likely move the potential problem to one of ensuring the safety of the passengers...
- afarrell 12y ago
  You are thinking of http://sawstop.com/why-sawstop/the-technology http://sawstop.com/why-sawstop/the-technology. The problem with your comparison is that cars already have brakes. Driverless cars would improve reaction time, but can't do anything to affect stopping time. You would need to activate some additional braking system. <snark>I also don't see how a car could dive below the roadway instantly. Roads don't have car-sized holes in them. Usually.</snark>
- EvanAnderson 12y ago
  Think about the physics. There's a _whole_ lot more energy in a moving car than in a saw blade. The car is also being operated in physical circumstances that vary wildly (wet road surfaces, high wind, being struck by other cars) that don't happen in the comfortable little micro-universe of a spinning saw blade.
- toothbrush 12y ago
  Wow, that's super neat, i'd never heard of it. Seems like something that should be absolutely mandatory for all factories equipped with such devices! Go technology! Here's a demonstration, it's very fluffy but it gets the point across. https://youtu.be/eiYoBbEZwlk https://youtu.be/eiYoBbEZwlk
darkmighty 12y ago
It's more complicated, since cars can steer, but it's still approx. function of speed^2/distance, but a lot more permissive. And then there's emergency coordination among vehicles to prevent the crash among the vehicles themselves too.

NovaS1X 12y ago

Yep! Latency and Inertia still exist with autocars. Anyone wishing to challenge physics may as well be awarded a Darwin Award.

Cakez0r 12y ago

I can't possibly work that out. The only answer is self-driving segways!

happyscrappy 12y ago

There is a table saw that stops the blade the instant it senses the capacitance of a finger. It completely ruins the saw but saves the finger. Something like that could work here if the car could see the pedestrian far enough in advance to stay within parameters. Ruins the road and the car not the pedestrian.

darkmighty 12y ago
If you stop the car instantly that's equivalent to a crash for the car occupants.
- afarrell 12y ago
  It is in fact a pretty jerkish thing to do.
jccooper 12y ago
Those jam an aluminum block into the blade. I'm not sure what the equivalent would be for a car. Perhaps you could line the bottom of the car with rubber and then blow the wheels off. But there's plenty of problems with varying road surface and conditions and having a system that's never used. But a decent brake system and tires can do 1G, which is pretty good. I suppose you could go to maybe 5G for a true emergency brake system (which would be pretty rough on the occupants, eyeballs-out), but it hardly seems worth the cost (in money, weight, maintenance, accidental triggering, etc.) compared to good sensors and the existing braking systems.
- pluma 12y ago
  I think the equivalent of jamming a block of solid aluminium into a spinning blade would involve some kind of anchoring. It would ruin the car and likely damage the road but as long as the passengers can be protected from the rapid deceleration, it just might save a life. OTOH you could just wrap the entire car in airbags and protect pedestrians the same way you protect the passengers. Not sure how practical or useful that would be, though.
- joncrocks 12y ago
  Yeah, and don't forget that the car has people in it too :-) While you can instantaneously stop a saw blade to save a finger, stopping a car 'quickly' will likely move the potential problem to one of ensuring the safety of the passengers...
afarrell 12y ago
You are thinking of http://sawstop.com/why-sawstop/the-technology http://sawstop.com/why-sawstop/the-technology. The problem with your comparison is that cars already have brakes. Driverless cars would improve reaction time, but can't do anything to affect stopping time. You would need to activate some additional braking system. <snark>I also don't see how a car could dive below the roadway instantly. Roads don't have car-sized holes in them. Usually.</snark>
EvanAnderson 12y ago
Think about the physics. There's a _whole_ lot more energy in a moving car than in a saw blade. The car is also being operated in physical circumstances that vary wildly (wet road surfaces, high wind, being struck by other cars) that don't happen in the comfortable little micro-universe of a spinning saw blade.
toothbrush 12y ago
Wow, that's super neat, i'd never heard of it. Seems like something that should be absolutely mandatory for all factories equipped with such devices! Go technology! Here's a demonstration, it's very fluffy but it gets the point across. https://youtu.be/eiYoBbEZwlk https://youtu.be/eiYoBbEZwlk

darkmighty 12y ago

It's more complicated, since cars can steer, but it's still approx. function of speed^2/distance, but a lot more permissive. And then there's emergency coordination among vehicles to prevent the crash among the vehicles themselves too.