Can Magnets Really Prevent Car Crashes? Debunking the Myth

[xxChrisxx]

As nice as this discussion is. Why on Earth would we need magnets and GPS to do it?

The S class already has the basic tools to do the job anyway. Adaptive cruise control, Radar sensor and conventional brakes. If it tracks an obect on a collisions course with a relative speed above a certain amount, the brakes will be applied.

It also has a system that mean you slam on it alters the braking force for you on gentle braking, not so much you get rear ended but enough so you don't crash. In the event of 'panic braking' ABS and brake assist systems work to reduce any collision speed.

Not totally foolproof yet but better than magic magnets and expensive satellites.

 

[MikeCB]

Hi, new here.

So let's say a car and truck were on collision courses with these magnetic bumpers equipped, wouldn't the trucks bumper field be higher than the cars? If so i could imagine the car being repeled downward and into a flip, at which point the car would pulled towards the trucks bumper, because once the car goes into a flip it exposes its metal parts to the trucks bumper field.

Did that make any sense? If so, does it work (in theory)?

 

[Redbelly98]

Welcome to PF.

Hi, new here.

So let's say a car and truck were on collision courses with these magnetic bumpers equipped, wouldn't the trucks bumper field be higher than the cars?

Not necessarily. That would depend on the strength of the magnets, which could be made the same for both cars and trucks.

If so i could imagine the car being repeled downward and into a flip, at which point the car would pulled towards the trucks bumper, because once the car goes into a flip it exposes its metal parts to the trucks bumper field.

Did that make any sense? If so, does it work (in theory)?

It is possible, in theory, that the cars lighter mass would make it prone to doing this.

 

[DaveC426913]

wouldn't the trucks bumper field be higher than the cars?

Not necessarily. That would depend on the strength of the magnets, which could be made the same for both cars and trucks.

He means wouldn't it be physically higher, i.e. as measured from the ground .

i could imagine the car being repeled downward and into a flip, at which point the car would pulled towards the trucks bumper, because once the car goes into a flip it exposes its metal parts to the trucks bumper field.

You raise an excellent point that should have been obvious earlier. The two magnets interacting would only bring the car to a stop if they were properly aligned and the vehicles were constrained to narrow paths. In all other case the magnets will still repel each other, true, but in a highly unstable way, not unlike bouncing a ball on top of another ball. And the momentum will be preserved.

The most dramatic and common effect would be to put the car(s) into a spin and thus completely out-of-control.

And yes, magnets that powerful will strongly attract the metal in the car, meaning the cars will slam back together.


I was foolish to think this idea had some merit. Anyone who has played with a couple of magnets, trying to balance then and bounce them off each other will know that it is a useless feat. They will spin and collide.

 

[Redbelly98]

He means wouldn't it be physically higher, i.e. as measured from the ground.

Oh! Thanks for clearing that up

 

[odmart01]

This is clearly not going to work out

 

[Jayanco]

The car magnet idea might not work, but I'm new to this and you all have sure made my brain work. :)

 

[abhishek ghos]

some mechanism which can measure the speeds of incoming cars, send signals, pulls up breaks and activates some magnetic repulsion, saves the day for two cars onto each other but there are other objects which can be a problem.
but the idea is cool and should be used in the time to come...

 

[ElCuabnito]

What if we lay out a thin layering of magnets around the bottom portion of the car, said layer would have a positive charge. And the we could modify the magnets by connecting them to the cars power so that the strength of the magnetic would be directly affected by the speed and power exerted by the car. We could also attach small sensors on separate areas of the magnetic layering so that if scrap metal does get attached to a section, then the power to that area would go to 0 and the scrap metal would fall off.

 

[Drakkith]

What if we lay out a thin layering of magnets around the bottom portion of the car, said layer would have a positive charge. And the we could modify the magnets by connecting them to the cars power so that the strength of the magnetic would be directly affected by the speed and power exerted by the car. We could also attach small sensors on separate areas of the magnetic layering so that if scrap metal does get attached to a section, then the power to that area would go to 0 and the scrap metal would fall off.

I believe page 1 explains the why the basic idea simply isn't feasible. The rest of the thread kind of hammers it in.

 

[OmCheeto]

What if we lay out a thin layering of magnets around the bottom portion of the car, said layer would have a positive charge. And the we could modify the magnets by connecting them to the cars power so that the strength of the magnetic would be directly affected by the speed and power exerted by the car. We could also attach small sensors on separate areas of the magnetic layering so that if scrap metal does get attached to a section, then the power to that area would go to 0 and the scrap metal would fall off.

Oh! I didn't know we had two magnets on car bumper threads.

I missed this one.

But I like your idea of collecting scrap metal with cars. Only I'd turn the magnets off when I got home. Scrap metal is valuable.

The linked thread above contains the calculations I performed on magnetic car bumpers.

And I did solve one of the problems mentioned in both threads with a Halbach array.

Though I still don't think they will prevent car crashes, I have come up with a different use for magnets in bumpers:

Tailgaters. When people insist on tailgating, they are psychologically pushing the car in front of them. Why not let them really do it, safely, with magnets! I'd be getting about 500 mpg if we could get these installed on everyones cars.

 

[lortech]

Obviosly the producers of Top-gear have no previous education in classical physics.


I never saw the episode but, there is no magnet that would offset the potentially huge amount of POTENTIAL ENERGY stored up in the mass x acceleration of the vehicle to offset any magnetic repulsion.

Now, if there was a large NEO magnet underneath the vehicle, that was suspended 1/4 inch off the ground, and the vehicle was at a constant rate of acceleration, then the car would slow down substantially if it were to transition from blacktop to a solid billet of aluminum it was moving over.

In Washington state, Department of Transportation do have trucks that have massive retractable crash boxes that do crumple in the event a car were to hit it. These are there to protect the workers.

BTW does anyone here have a good source of Rare Earth Neo magnets of different sizes that is very competitive in price?

 

[Low-Q]

No question, I just wanted to share a thought...

I saw a very old episode of Top Gear last night, where he put magnets onto the front of two model cars, and drove them at each other. Because the magnets were orientated so that they would repel, the cars couldn't crash.

This was given as a way of preventing accidents.

However, if this was done with real cars, although the cars wouldn't touch each other, they would sustain just as much damage as if they had hit.

It would be pretty hard to drive east or west with 500kg neodymium magnets in the front

Instead, use a 1 meter thick block of EPP foam

Vidar

 

[NanaToru]

My initial thought was... wouldn't giant magnets like that mess with cell phones and heart monitors anyway?

 

[OmCheeto]

It would be pretty hard to drive east or west with 500kg neodymium magnets in the front

Instead, use a 1 meter thick block of EPP foam

Vidar

500 kg!

By my calculations, from my $800 6" diameter x 2" thick magnet, that would cost roughly $400,000!

Calculations on how to fit all those magnets(500!) on a vehicle not attempted.

56.5 cubic inches for a 6" x 2" magnet
7.00 specific gravity of neodymium
0.0164 weight of 1 cubic inch of water in kg
6.49 kg of $800 magnet
500 kg of magnets on Vidars car
506 magnets
$405,189 never mind

 

[sophiecentaur]

Did anyone consider the extra MASS that would be involved for a strong enough magnet?
If this idea was on TV it must have been April 1st, I think.

 

[Khashishi]

Permanent magnets won't do. But, how about an electromagnet that turns on when a crash is occurring? But, it would require a pulsed energy supply with an energy comparable to a car crash, over a few milliseconds. Then some dude decides to hack the energy systems into a railgun power source...

 

[Drakkith]

Permanent magnets won't do. But, how about an electromagnet that turns on when a crash is occurring? But, it would require a pulsed energy supply with an energy comparable to a car crash, over a few milliseconds. Then some dude decides to hack the energy systems into a railgun power source...

No, the entire idea of using magnets to make an accident safer is completely bogus. Other than the fact that it isn't going to work, for the cost, weight, and complexity of such a system you could simply add passive features that would actually save lives.

 

[Khashishi]

I know. I was just playing around with the idea of having railgun power sources on every car.

 

[Arpiet]

Stop behaving like small kids you don't have a very simple idea
you all mean that if we place a net of magnet over the cars then due to the force of repulsion the cars will not collide but on the same hand the another pole exposed to the another side will attract the different pole and that could be a cause for the accident but my sweet companions if you place two magnets in such a way that their same pole (south pole) will face to every internal face and due to this all the cars will only have the north pole exposed to the outer and that will only prevent accident not it'll going to cause it :-)

 

[Drakkith]

Stop behaving like small kids you don't have a very simple idea
you all mean that if we place a net of magnet over the cars then due to the force of repulsion the cars will not collide but on the same hand the another pole exposed to the another side will attract the different pole and that could be a cause for the accident but my sweet companions if you place two magnets in such a way that their same pole (south pole) will face to every internal face and due to this all the cars will only have the north pole exposed to the outer and that will only prevent accident not it'll going to cause it :-)

I highly advise you to re-read the thread. It has already been explained that this concept is fundamentally flawed and will not work.

 

[Dale]

Hi Arpiet, welcome to PF!

if you place two magnets in such a way that their same pole (south pole) will face to every internal face and due to this all the cars will only have the north pole exposed to the outer

No, this arrangement would be a magnetic multipole, not a monopole. Other similar magnetic multipoles would be drawn to the joint between the two south poles. It would cause collisions if strong enough, and it would make them into side impact collisions where there is less of a crumple zone available.

 

[OmCheeto]

Hi Arpiet, welcome to PF!No, this arrangement would be a magnetic multipole, not a monopole. Other similar magnetic multipoles would be drawn to the joint between the two south poles. It would cause collisions if strong enough, and it would make them into side impact collisions where there is less of a crumple zone available.

This is why we need to spend billions of dollars on research so we can find magnetic monopoles. We would then just super-glue quadrillions of them to the exteriors of our vehicles.

While we're waiting, why don't we just negatively charge all the cars, with some unknown number of coulombs of electrons.

Hmmm... That won't work. When the cars approach each other, the electrons will simply race to the opposite ends. Ah ha! But that's only with metal cars. If we make them out of some type of insulating material, it might work. Or electrically charged paint!

hmmm...

In everyday terms
...
According to Coulomb's law, two negative point charges of 1 C, placed one meter apart, would experience a repulsive force of 9×109 N, a force roughly equal to the weight of 920000 metric tons of mass on the surface of the Earth.

Well that sounds like plenty of force. But obviously, cars aren't point sources. I suppose we could model cars as spheres, just to make the math simpler.

skreeeeetch!

This isn't going to work at all. Half of the population is not going to get into these cars after they spent all that money on perms.

Never mind...

ps. People just need to learn how to drive, properly...