# A Magnetic Question

Hi all
i literally just joined and hope that some if not all the questions i have can be answered, but for now this one is the one i need answering

Q: i have a body floating above a magnetic surface, behind it is a post with a permanent magnet attached, the floating body has a magnet also fixed to its rear, both poles are repelling each other, if i affix the body as close to the post as possible and then release it, what distance will the body travel?, taking into account there is no contact friction as the body is floating above the ground and the grade of neodymium magnet is N52.
I hope i explained the question clearly enough, not being technically minded i am at a loss top work out the equation to find the answer, thankyou in advance.
Levi

You're missing way too many details to answer that. Perhaps you could be more specific.

If we're ignoring all friction losses then it will never stop, but then there's air resistance which means we need more details for that.

What about the mass of the body? That will effect the initial acceleration.

Jarednjames
my apologies, wrote that at 4 in the morning so wasn't thinking, ok the body is small, 20 cm in length 15 cm wide and 10 cm high, it weighs practically nothing, basically a plastic strut, i wish i knew how to calculate the mass, but as far as i can be sure it will be very very light, the air resistance is still a factor but the object will be aerodynamic in design, it isn't for this purpose but it will be,

The body will travel until air resistance causes it to stop. Without knowing the strength of the magnets and the mass of the vehicle it really is impossible to tell.

The principle you are talking about is the same used for maglev trains. They constantly provide a pushing force and so the train keeps going without only wind resistance acting against it.

thankyou jarednjames
thats what i was thinking, as i am not very technically minded i cant give you the strength of the magnet, only the N grade, which is 42, but im guessing that isn't much help, as i said you answered my question enough to look at that as a realistic propulsion means.

thankyou jarednjames
thats what i was thinking, as i am not very technically minded i cant give you the strength of the magnet, only the N grade, which is 42, but im guessing that isn't much help, as i said you answered my question enough to look at that as a realistic propulsion means.

Well, no. It isn't a realistic propulsion means by any stretch of the imagination. It only provides force for a very short amount of time and once it's travelled a relatively short distance there it's constantly slowing.

I recommend you look up how a maglev works to understand what it takes to use magnets for propulsion.

Levi_tation,

As jarednjames is suggesting, magnetic levitation and magnetic propulsion are tricky things to engineer. You might read through this:

http://en.wikipedia.org/wiki/Magnetic_levitation

and NOTE:

Earnshaw's theorem proved conclusively that it is not possible to levitate stably using only static, macroscopic, paramagnetic fields. The forces acting on any paramagnetic object in any combination of gravitational, electrostatic, and magnetostatic fields will make the object's position unstable along at least one axis, and can be unstable along all axes.

The use of electromagnets or super conductors are required for true stable levitation.

Fish