Friction from air
Even air creates friction—it rubs against moving things and slows them
down. You can make a \”helicopter” that uses the friction of air to slow
its fall—and to spin, too.
Place the paper with the short edge toward you. Fold the paper in half
the long way. Open the paper. Fold the bottom corners in until they meet
at the center crease. You will have two folded triangles at the bottom
of the paper. Next, fold the outer edge of each triangle in as far as
the center crease.
Hold the folded paper straight up and down. Let it drop. Does it fall
fast or slowly? Here is something you can do to slow it down.
Measure one inch (2.5 centimeters) up the center crease from where the
folded edges meet and make a mark. Cut along the crease from the top
down to the mark. Fold the paper on one side of the cut forward. Fold
the other side back. Now your \”helicopter” has flaps.
Drop your \”helicopter” again. This time it falls gently, spinning as it
goes. The air rubbing and pushing on the two flaps makes all the
difference.
Materials
• paper (8V2 x 11 inches;
21.5 x 27.5 centimeters)
• ruler
• scissors
