65
At the heart of this trick
is a force called friction.When objects rub against each
other, friction makes it harder
for these objects to move. This
force is stronger when you push
two things together—the harder
you push your hands together,
for example, the harder it is for
them to slide apart. Since the rice
in your friend’s bottle doesn’t
push much against the chopstick,
the chopstick slides out. The
tightly packed rice in your bottle,
however, does push hard on the
stick. This greater friction stops
the chopstick from sliding out...
and you can pick up the bottle!SCIENCE
PART...
THE
With the bottles
prepared, you can now
challenge your friend.
Push your chopsticks
into the bottles. When
you lift your chopstick
up, the bottle will also
rise up, but your friend’s
chopstick will slip out.4
Don’t put any more rice
in the second bottle. This
will be your friend’s
bottle in the trick.Add more rice to this
bottle until it’s full to
the top again. Keep
repeating steps two
and three until you
can’t fit any more rice in
the bottle. Don’t let
your friend see you
preparing the bottles!3
Tightly packed
rice means a lot
of friction.Loosely packed
rice means
little friction.US_064-065_Chopstick_challenge.indd 65 12/09/2018 15:50