Preparing the magnet
It is important that the magnet does not tumble
while it is falling (rotation about a horizontal
axis), because it will generate unpredictable
voltage signals that will be difficult to analyse.
Three ways to prevent tumbling are shown
in figure 6: stacking a few magnets together
(figure 6(a)), gluing a dowel to the magnet
(figure 6(b)) or gluing a drinking straw to the
magnet (figure 6(c)). A folded cloth (1 cm
thick), a piece of thick cardboard or an offcut
of carpet should be used as a landing pad to
protect the brittle magnets when they fall out of
the bottom of the pipe.