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Magic Sand Wand™ -
Solve the mystery of the sands!
The Physics of the Magic Sand Wand®
The trick is to get the ball from one end of the wand to the other,
through the sand. One might think that since the steel ball is much
more dense than the sand, it will sink to the bottom when the sand is
agitated.
The opposite is actually true: Hold the wand vertically with the
ball at or near the bottom. As you shake the wand up and down, the
ball will actually rise through the column of sand. Each time the wand
is jerked upwards, both the ball and the sand move up at the same
speed. Because the sand particles are lighter and smaller, they
experience greater relative friction than the steel ball when rubbing
against each other. This causes the sand particles to slow down
faster.
After each shake, more sand particles are packed underneath the
steel ball, until it magically emerges from beneath the sand.
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