Magnetism used as a repulsive force

[Pr1mals]

Is it possible to create such a strong repulsive force using 2 magnets that it can essentially keep these 2 objects from touching each other? Basically if there are 2 objects coming at very high speeds if both of these objects had a magnet on them that can create such a strong repulsive force could that be used to make it that these two objects do not touch each other?

 

[BvU]

Hi,

!​

It will be difficult if the objects are relatively heavy. And you have to do something to prevent one of them flips and is attracted by the other magnet.
Experiment !

 

[anorlunda]

Obviously, the answer is yes and no. If their relative speed is slow enough, yes. If too fast, no.

Imagine a magnetic levitation train that hits a bump. Will it touch the rails? It depends on the speed of the train and the dimensions of the bump.

 

[Keith_McClary]

One magnet and a copper block:


Edit: A perfect conductor acts as if a there is a mirror-image magnet inside it. With copper, as the field penetrates it, a current is induced. Some energy is absorbed because of the resistivity of the copper.

 

[DaveC426913]

The problem with magnetic repulsion is that it falls off as the cube of the distance. For every doubling of the distance, the force falls off by 8 times. i.e. the repulsion at 12 inches is 1/8 of that at 6 inches. The repulsion at 24 inches is 1/64th that at 6 inches.

Thus the effect is virtually negligible at any meaningful distance.

 

[sophiecentaur]

It may help to look at the Work involved, rather than Force (the old favourite). The Kinetic Energy needs to transfer to Work against 'something'. To act as a brake, a mechanism needs to apply a force over a relatively long distance and the distances involved as you get close enough to a magnet are not enough.
Otoh, an Eddy Current brake can apply a relatively low force over a long distance and hence, dissipate a useful amount of energy. (Force times distance). The only snag with eddy current braking is that the braking effect depends on relative speed, so it decreases as you come to a halt.

 

[alan123hk]

Is it possible to create such a strong repulsive force using 2 magnets that it can essentially keep these 2 objects from touching each other? Basically if there are 2 objects coming at very high speeds if both of these objects had a magnet on them that can create such a strong repulsive force could that be used to make it that these two objects do not touch each other?

It does not seem to be so difficult to make a DIY magnetic levitation system, and the suspended object in the system do not need to rotate at a high speed to maintain its stability.

But I don't know if the two objects moving at very high speeds will make it very difficult to achieve stable levitation.

 

[sophiecentaur]

It does not seem to be so difficult to make a DIY magnetic levitation system,

I already made the point that Braking involves getting rid of a lot of (Kinetic) Energy. That involves Work, which is Force times Distance moved. However high a Repulsive Force you can obtain with two magnets, it only works over a short distance and you can't dissipate or store significant energy over such a distance.
If you're going to understand Physics then you have to consider the relevant factors. People seem always to want to talk in terms of Forces when on many (most?) occasions it is the Energy of a situation that needs to be considered.
Taking a more Mechanical situation, we often use sandbags, rather than steel plates to deal with explosions. That's because the work done in slowing bullets and shrapnel uses a relatively low force over a long distance in the sand. A bullet bouncing off a steel plate can still do damage. Of course, steel armour is more convenient to carry around on a tank than a pile of sandbags. The noise inside a tank can be horrific as shells bounce off it; some of the Energy still gets through.