Question

jolie builds a model of a maglev train. she uses disc magnets to levitate the train. a disc magnet has its north and south poles on its faces, as shown.
image of a disc magnet with n on top face and s on bottom face
what is the best way to arrange the magnets on the train and on the track so that the model train levitates?

• flat, so that the north pole of each magnet on the train points up and the north pole of each magnet on the track points up
• flat, so that the north pole of the magnets on the train point up and the north poles of the magnets on the track point down
• on edge, so that the north poles of the magnets on the train point to the front and the north poles of the magnets on the track point toward the rear
• on edge, so that the north pole of each magnet on the train and on the track point toward the rear of the train

Explanation:

To levitate the train, magnetic repulsion is needed (like poles repel). For disc magnets with poles on faces, arranging them flat: train magnets' north up and track magnets' north down (so train's north faces track's north, repelling). Other options: same - pole - up (attract, wrong), on - edge arrangements (involve magnetic attraction/parallel fields, not levitation - causing repulsion). So the correct arrangement is flat with train north up and track north down.

Answer:

B. flat, so that the north pole of the magnets on the train point up and the north poles of the magnets on the track point down