# Calculating the Attraction Speed of Magnets

• Electrica
In summary, there is no set formula for how fast magnets attract, but you can find the velocity before and after they collide depending on how close you are to them.
Electrica
Hi PF Pros... I wonder if you can help me...

I am trying to see if there is a formula for how fast magnets attract. I know that there is the inverse square in terms of power loss and that magnetism is a field that travels at or near light speed.

But, for example, if I have 2 cyllander NIB magnets (.5" wide x 1" long) with 5,000 Gauss each and they are 3 inches away from each other... at what speed will they meet? If I have the speed I can calculate the time/distance. (as for weight or other forces like friction, etc, please feel free to make something up for the equation).

Thanks!

~Electrica

No, there probably isn't a formula for this velocity.

If anything, you might be able to find the force between two magnets, however it is very dependent on the spacing between the magnets.
So, you would only have to move the magnets closer to each other by a small amount and they would be attracted to each other a lot more.

There is a formula for this attraction here: (formula taken from Wikipedia article on magnets)

where

B0 is the magnetic flux density very close to each pole, in T,
A is the area of each pole, in m2,
L is the length of each magnet, in m,
R is the radius of each magnet, in m, and
x is the separation between the two magnets, in m

relates the flux density at the pole to the magnetization of the magnet.

Probably easier is to just measure the force with the following method:
http://www.exo.net/~pauld/activities/magnetism/forcebetweenmagnets.html

Well, there will be a potential energy due to that force that looks like the integral of Fdx, so you can set that integral equal to the kinetic energy when they collide (1/2 mv^2) and you will find the velocity right before impact (neglecting friction)... should be able to repeat this to find the velocity after traveling half the distance, etc. etc.

But if you are holding them close, and you want to find the velocity right when you let them go, then... I'll think about it...

Thanks a lot! I'll try that. Please do let me know if you come up with the other. -Electrica

mordechai9 said:
Well, there will be a potential energy due to that force that looks like the integral of Fdx, so you can ...

Thank you very much for this info! I have some reading to do! - Electrica

vk6kro said:
No, there probably isn't a formula for this velocity.

If anything, you might be able to find the force between two magnets, however it is very dependent on the spacing between the magnets...

## 1. How do you calculate the attraction speed of magnets?

To calculate the attraction speed of magnets, you need to measure the distance between the two magnets and the initial velocity of the magnet being attracted. Then, you can use the formula F = (m1 x m2) / d^2 to calculate the gravitational force between the two magnets. This force will determine the attraction speed of the magnets.

## 2. What factors affect the attraction speed of magnets?

The attraction speed of magnets is affected by the strength of the magnets, the distance between them, and the initial velocity of the magnet being attracted. The type of magnet material and the presence of any external magnetic fields can also impact the attraction speed.

## 3. How can I increase the attraction speed of magnets?

To increase the attraction speed of magnets, you can use stronger magnets, decrease the distance between them, or increase the initial velocity of the magnet being attracted. You can also use magnet materials with higher magnetic permeability, which will enhance the strength of the magnetic field and increase the attraction speed.

## 4. What units are used to measure the attraction speed of magnets?

The attraction speed of magnets is typically measured in meters per second (m/s). However, it can also be measured in other units such as centimeters per second (cm/s) or miles per hour (mph), depending on the specific experiment or application.

## 5. Can the attraction speed of magnets be calculated for all types of magnets?

Yes, the attraction speed of magnets can be calculated for all types of magnets as long as the necessary measurements and variables are known. However, the results may vary depending on the strength and characteristics of the specific type of magnet being used.

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