Repulsion force between two magnets

In summary, the two magnets will have a force of repulsion between them, which will be inversely proportional to the distance between them.
  • #1
Vic88
1
0
If I used two magnet, each being able to lift a load of 100 lb, to repel each other, what will be the total repulsive force ?
 
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  • #2
On what basis...?IIRC,the empirical formula of Coulomb gives a ~1/(r^2 ) interaction force.

Daniel.

EDIT:Why did you delete your post...? :bugeye:
 
  • #3
deleted post because I ignored all other fields lines

Physics is not my speciality but I believe that this may be an answer:

How far away are they?

Lets presume it is x.

The forces will interact at every point of x. If we take an arbitary point p, it will be y from one of the magnets, and 1-y from the other.

As we move the point y from one magnet to the other, we generate an inifinite number of points of repulsion.

As repulsion decreases at [tex]\frac{1}{r^2}[/tex], the sum is always,

[tex]\frac{m}{y^2} + \frac{m}{(1-y)^2}[/tex]

(where [tex]m[/tex] is the magnetic force @ 0 distance)

y equals 0-1 as it moves from one magnet to the other, so the solution is the sum using the values of y 1 to 0 as limits.

I think. some physicist will tell you there is a better way but I reckon by using common sense that is pretty close! :biggrin:

And there you go - a physicist did!

Regards,

M
 
Last edited:
  • #4
Can it lift 100 lbs. of paper? Might sound stupid, but the point is that the amount you lift depends on the material you are lifting. So the two (what you can lift, and force of repulsion between magnets) are unrelated.
 
  • #5
krab said:
Might sound stupid, but the point is that the amount you lift depends on the material you are lifting. So the two (what you can lift, and force of repulsion between magnets) are unrelated.

It also depends on temperature. I saw a demonstration where a material was dipped in liquid nitrogen then placed over a magnet. The supercooled material floated over the magnet for maybe a minute until it heated up, then it dropped as if somebody cut a string holding it up.
 
  • #6
Isn't it surprising that a question that should have a simple answer, doesnt?

I like E&M, but the way physicists understand magnetism is ovbiously inadequate for even the simplest situations involving permanent magnets.

I wish there was a simple theory of magnetism which could be applied to the real world, instead of magnetic fields and V x B forces (which I love, but are useless in all but the simplest geometries). Yes, it is possible to answer these questions using standard E&M, but it strikes me as a square peg - round hole type of problem.
 
  • #7
If each magnet can pick up 100 pounds of a high mu metal, then the repulsive force if you try to push them together is 100 pounds. The high mu metal becomes magnetized so that it has the magnetization M of a magnet of the same strength as the one picking it up.
 
  • #8
ShawnD said:
It also depends on temperature. I saw a demonstration where a material was dipped in liquid nitrogen then placed over a magnet. The supercooled material floated over the magnet for maybe a minute until it heated up, then it dropped as if somebody cut a string holding it up.

You need to be a bit careful here because what you saw might possibly be a superconductor (probably YBCO) and a magnet. This is a different concept that what is being asked in this question, I believe.

Zz.
 

Related to Repulsion force between two magnets

1. What causes the repulsion force between two magnets?

The repulsion force between two magnets is caused by the interaction between their magnetic fields. Each magnet has a north and south pole, and opposite poles attract while like poles repel. When two magnets are brought close together, their magnetic fields interact and create a force that pushes them away from each other.

2. How does the distance between two magnets affect the repulsion force?

The repulsion force between two magnets is inversely proportional to the square of the distance between them. This means that as the distance between the magnets increases, the repulsion force decreases. So, the closer the magnets are to each other, the stronger the repulsion force will be.

3. Does the strength of the magnets affect the repulsion force?

Yes, the strength of the magnets does affect the repulsion force. The stronger the magnets, the stronger the repulsion force will be. This is because stronger magnets have a larger magnetic field, which results in a stronger interaction and a greater repulsion force.

4. Can the repulsion force between two magnets be turned off or reversed?

Yes, the repulsion force between two magnets can be turned off or reversed by changing the orientation of one of the magnets. If one magnet is rotated so that its north pole is facing the other magnet's north pole, they will attract instead of repel. Alternatively, if one magnet is flipped over so that its north pole is facing the other magnet's south pole, the repulsion force will be turned off.

5. Why does the repulsion force between two magnets decrease over time?

The repulsion force between two magnets can decrease over time due to a phenomenon known as demagnetization. This is when the magnetic domains within a magnet become randomly oriented, resulting in a weaker magnetic field. This can happen naturally over time, or it can be caused by external factors such as heat or strong magnetic fields.

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