Physics Q (x post)

[jkkkk]

There are two magnets stuck together through magnetic force but there is a pane of glass seperating them, when I spin the magnet closest to me clockwise, both of the magnets spin and move to the right and down, when I spin them anti-clockwise, they spin and move to the left and down.

The magnets are side by side, and the force applied to make the magnets spin is irrelevant since I have spun them in different ways and from different angles and the result is always the same. They also spin in perfect sync.



Could someone please summarise the forces involved that make the magnet either shift left or right in both scenarios, I'm pretty sure I already know the answer, but one of my friends disagrees.

[PairTheBoard]

Because the force of atraction is strongest locally?

PairTheBoard

[PairTheBoard]

I change my answer. It's because of the polarity. They stay alligned with opposite polarities next to each other.

PairTheBoard

[jkkkk]

Explains nothing, please expand.

[MediaPA]

I'm really struggling with this because seems that everything balances (except a resultant effects of the spin itself). Going with the perfect spin (magnets perfectly aligned 100% of the time)

Friction should balance throughout the system. The angular velocity at any point on one half of the magnet system = the angular velocity at the reflected point (opposite direction). And friction being the result of Kinetic energy *coefficient of friction

EMF forces would also seem to balance in a similar way (NS::SN alignment so they are attracted to each other through the glass).

The spin seems to be the only reason as it is a tendency in other spinning object systems. IE spin a ball in place, push it forward, it will exibit the same tendency, going in the direction of spin.

A curveball manages to create a high and low pressure zone which moves the ball in the air as it goes to the plate, causing it to break.

Basically, I'm just being really stubborn on my thinking in this situation as to what force is not balanced resulting in the movement.

[Siegmund]

I would guess, and it's only a guess, that your thumb and forefinger don't apply perfectly equal amounts of force to opposite ends of the magnet, and impart a net acceleration to it.

You can test the theory by spinning ONE magnet on a flat surface, with the same hand motion. Guess: whether one or two magnets, clockwise or counterclockwise, the magnets move the direction your thumb pushed them. (Additional guess: you are right-handed.)

[J.A.Sucker]

The magnets stay parallel to each other "in sync" because they want to be aligned as such (think about the poles in a magnet - the North of one magnet wants to be near the South of the other and vice versa). This is going to always be true for the pair, so if you spin one, the other will track it.

The second half of the question is about torque and gravity. Before you spin the magnets, they are at equilibrium - there's enough friction between the magnets' coatings and the glass that the attraction between the magnets lets them stick together on the glass. If the glass or coating of the magnet was more slick, then they may just drift down spontaneously.

Once you start spinning them, the magnet pair always moves down once you disturb this equilibrium due to gravity and due to the torque that you apply to the system, combined with the magnetic force field lines that are radiating from the magnet pair. If you could spin them fast enough, you could impart enough torque to pull them upward first, but that may be tough here becasue the magnetic fields are present. This is actually the trickiest thing to think about, but basically the magnetic fields extend out away from the magnets and they serve as a guide for the magnet pair. If you spin it clockwise, you tap into the one that would pull the magnets "right" and if you spin it counterclockwise, you tap into the field line that pulls it "left." Again, since the system starts in a delicate equilbrium, you can tap into either path depending on which way you spin them. The reason that the magnets slip and move down is because frictional forces are always harder to overcome at the beginning, but are easier to maintain movement on - kind of like watching me get off my ass to get a beer on a Sunday afternoon. Once I get off the couch, I can get to the fridge quickly, but that initial momentum is the hardest. Same thing here - once you spin the magnets, there's enough momentum for gravity to overcome the frictional force.

There ya go.

Dr Sucker

[jkkkk]

How on earth does tapping into one magnet pull them both to one side, and how exactly, am I tapping into one magnet by spinning them either way.

[J.A.Sucker]

What's really happening is the field lines radiate out from the pair of magnets in a toroidal-like pattern. They go from one end to the other. If you spin it one way, you are starting momentum in this direction and are keying into the fields that have that handedness; if you spin it the other way, you key into the other field lines.

This is the answer, BTW, and would be easier to describe wtih a picture, but I'm not posting one.

[m_the0ry]

This doesn't have anything to do with magnetostatics as far as I can tell. This is an effect of gravity. The spinning magnets tilt towards earths gravity (down) and put more friction between the surface there, meaning more force on the bottom half of each part of the rotation at the glass/magnet interface, causing it to move right when spun clockwise and left when spun counterclockwise. Just like a wheel.