# Repulsion of magnets

1. Feb 6, 2015

### eric davis

Ok I have a question that I cannot find a answer anywhere on the Web for so I'm gonna try to explain it best I can. So if I stacked 10 magnets in a plastic tube, s-n-n-s-s-n-n-s-s ect...... and each magnet had a repel of 10lbs, would the total repel be 10 pounds when compressed or would it be 100lbs compressed? Or is it like when u stick two magnets together to they loose much of there strength? This has my head hurting.

2. Feb 7, 2015

### Bystander

Do you mean ten pounds will "force" contact between two magnets? If so, place the ten pound force against the top magnet in your stack while holding the second in a fixed position --- do they contact? Release the first pair supporting the ten pounds while holding the third fixed --- do the first two magnets plus the ten pounds contact the third?

3. Feb 7, 2015

### eric davis

Ok I hope I'm saying this right, I think ur saying what I'm saying but the magnets will be like this in a tube free floating to make like a spring;

n-s (10lbs repulsion) s-n (10lbs repulsion) n-s (10lbs repulsion) s-n.

Now the first magnet is stationary with the other 3 on top in a tube. All repelling each other. Now wen u take just say a pencil, push on the top magnet downward, will this create a spring effect equal to 30lbs? I know when you do only two magnets of equal strength, the resistance is equal. Like one 10 pound to another 10 pound you only get 10 pounds of resistance. But I'm talking about 3 gaps that have to be compressed. I hope that made sense......

4. Feb 7, 2015

### 256bits

We can re-write that as somewhat symbolically:
F0-->N1S1<--F12-->S2N2<--F23-->S3N3<--F4

We can do some analysis:

F0 and F4 are the forces on each end of the line of magnets.
Since the whole line of magnets does not accelerate after we have applied the end forces, we can conclude that F0 = F4.

Similarily, since magnet 1 does not accelerate after we have applied the end forces, we can conclude that F12 = F0.

Continuing, we can say F23 = F12, and F4 = F23.

What does that tell you about the applied force will be just enough to close all the gaps between the magnets?

5. Feb 8, 2015

### eric davis

Thank you!!! That does make sense! OK so let's say in a shock that's used in a truck suspension, and in the shock was spring loaded. Take out the spring and replace it with 10-20lbs magnets the total repel force will only be 20lbs then. Thus us exactly what I needed to know.