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Aha! yes the magnetic field is only at the ends.
Here is one from the net...
A Ping-Pong Ball in a Hole
Your last good ping-pong ball fell down into a narrow metal pipe imbedded in concrete one foot deep.
How can you get it out undamaged, if all the tools you have are your tennis paddle, your shoe-laces, and your plastic water bottle, which does not fit into the pipe?
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