Flying an air-filled water balloon with a straw is child's play.
Trying to explain how it flies can be a physics professor's
worst nightmare. Grab a balloon and a straw and step into the
fiendishly complicated world of fluid dynamics, if you dare. 1.
Inflate a water balloon with air and tie a short piece of string
or wool (around 10 centimetres) to the knot. Add a tiny piece of
plasticine or poster-hanging putty to the end of the string.
(The more you add, the harder you'll have to blow, so not too
much!) 2. Rotor blades are optional and will cause your balloon
to spin. Without them, it will just hover. Make each rotor blade
by cutting off a small piece of sticky tape (about
1.5-centimetres long). Bend and press the tape together so that
the sticky side sticks to itself, leaving two small tabs to
stick to the balloon. 3. Stick the rotor blade you made in Step
2 to the balloon at a 45° angle. 4. Repeat Steps 2 and 3 for a
total of four rotor blades evenly spaced around the balloon's
circumference. When air pas