How much force is required to seperate magnets?
823892
In this reference, http://en.wikipedia.org/wiki/Magnets near the end of the article there is a formula for the force between bar magnets very close together.  You wll need to know the magnetic field strength of the magnet.  Also, for sliding, you will need to know the coefficient of friction.
761342
We did something like this in my physics lab with an Atwood machine.  It was a pully with weights hanging from it.  I can't exactly remember how it worked, but maybe this will inspire you.  We also did something with an air track and these two masses colliding and we'd see which one would go in which diretcion.  You need a nearly frictionless surface, like an air hockey table or ice slab.
703613
If they are too strong to pull apart directly, try sliding them.\n\nIf this doesn't work, find an even stronger magnet and put something between it and the other two first.
784877
How are they applied? Tangentially? In opposite direction? Or same?\nLet us assume oppo direc and on the border.\nThen net force=35N.\nTorque = r x F = I w\n=35x0.341= ''0.5'' m R^2\nR radius m mass\n ''Check if it is 0.5 only for a solid disk or cyliner about its axis.\n\nHope it helps
800493
Pounding on your workbench can put very high shock loads throughout.  In extreme cases shock waves can cause pieces of solid steel to separate (called spalling).  Further, as other answers mentioned, magnets tend to be brittle.  This is not because they are made of cheap iron.  Modern rare earth magnets are made using a complex sintering process where particles are compressed at slightly elevated temperature to hold them together.  They are notoriously brittle.  Finally, internal forces caused by the fields inside the magnet actually tend to force the magnet apart, splitting it from pole to pole.  Put this all together and poof - one magnet becomes several.
531203
prooly need ifrared thingy\ntry a industrial magnet
702587
It won't be easy to calculate.  You can easily calculate the strength of the magnetic field of the electromagnet with the current and the number of turns.  But it's harder to know the field strength of the bar magnet, and even harder to calculate the force produced by the interaction between the fields.  Once you got that force, it's easy to compare that to the gravitational force on the mass of the bar magnet.  It's probably easier just to build it and try it.  All you really need is a coil of wire and a current.\n\nOnce you have the apparatus, borrow an instrument to measure the fields.  I'd have more fun with a ball bearing on a circular (non-magnetic) track, timing the current to make the ball move around the track, like a cyclotron.
253070
Around any magnet there is a magnetic field.  The magnetic lines of force start from North Pole of a magnet and go around the magnet and ends in the South Pole.\n\nIf any isolated unit North Pole placed in that field will go round the magnet along a line of force in the direction of North Pole to South Pole and reach the South Pole.\n\nA unit South Pole will move in opposite direction.\n\nTherefore if another magnet is placed near it, its north pole tend to go along the line of force i.e. from North Pole to South Pole whereas the South Pole moves toward the North Pole on the opposite direction. \nThis is the mechanism of repulsion.
152782
If a bar magnet breaks into two, then there will be two magnets, each with a N and a S pole.
118123
There is a force applied to the permanent magnets equal to the force applied by the armature, but since the permanent magnets are usually attached to something huge they don't move much.  So there is little work done on them and so they don't eat up power.\n\nIt's just like asking "if I stand facing a wall and use my arms to push away from it, where did the power go in the wall".  It barely moves, so it absorbs very little power.\n\nSome power does go into the permanent magnet, due to the effects mentioned in the answer above, but it is generally small.
426889
Antigravity, but that hasn't been proven.  Magnetism works when you have two magneticaly charged objects.
105221
Well, the easiest way is to get some wire, wrap it around a iron/steel rod, and apply a current to the wire.\n\nTo get an electromagnet to have a lifting capacity that you specified, it will require a little more engineering work.  Trying to stay in the most basic terms, the power of your magnet will depend on how much current you put through the wire, how many turns you have around the iron rod, and something called the magnetic permeability of the iron rod.  Now there's some trade-offs with all of these factors.  More turns increases the magnet flux (strength), but requires more wire and increases the resistance.  More resistance means that you will need more current to counteract this problem.  Treating your electromagnet strictly as a resistor (which it is not), by following Ohm's law, you increase the current by increasing the voltage.   Too much current and you may end up melting your wire.   You want to keep the wire as small as possible so that you can get the turns as close as possible to your iron rod, but smaller wire has a higher resistance and lower current carrying capability.\n\nIt's a matter of balancing a lot of equations to get the best combination.  Your best bet is a little trial and error.
985642
You try what the first poster suggests, but it isn't likely to work well. Besides the danger mentioned of doing damage to the equipment, you will have one of these problems that will prevent the result you want:\n1) the electromagnet won't be strong enough to have any demagnetizing effect at all, \nor,\n2) the electromagnet will completely demagnetize the permanent magnet.\n\nUsually magnetic catches consist of a flat steel plate that seats against two poles of the magnet. A better solution is to put a few layers of tape on the steel plate so that it does not come into contact with the pole pieces. Depending on the kinds of tape you have around, one layer might be enough.\nMagnetic force falls off very rapidly as you separate the surfaces.
343621
Try googling "magnetic levitation circuit"\n\nHere is one of the many hits I got.
975911
First of all, I'm not professional of physical. I don't know at all, but Iron and steel are really high permeability, and strongly attract to magnet. Seem like the steel bar would tell you which one rely force electron. I don't think Iron has any thing to do with steel.
35844
Log on to http://en.wikipedia.org/wiki/Magnet\n\nand check out Characteristics of magnetic materials
19579
magnetig breaking can be done in 2 ways.  like the electric cars you see you can use the natural magnetic force to generate electricity while the car is rolling but decellerating. the natural resistance will slow the car.\n\nmore effective is what they use to propell and stop maglif trains.  they use electro magnets not permanent magnets i assume you know oposites attract and likes repel. N= north S= south \n\nN+N repel \nN+S attract\n\non a permanent magnet you have to turn the actual magnet to repel or attract the other\n\nin an electro magnet you need only reverse the electro magnetic field.  basically \n\nso when you have a series of magnets all in a row you rapidly switch the field back and forth in time with the passage of the magnets over the other magnets.  to make the train go you turn the magnets polarity so it pulls to the south pole of the other magnet then as it passes you switch the magnet around electrically so it pushes away from the magnet it was just pulling towards.  electric breaking is just the oposite. as the magnets aproach you turn N toward N and as they pass you turn one so they become N to S  the approaching magnets push against eachother thus causing MAGNETIC RESISTANCE then as they pass you switch one so as they seperate you need more energy to seperate them thus slowing the vehicle.\n\n\nI know it was hard to follow but without being able to actually show you it is hard to explain