|How Do Yo-Yos Work?
Yo-yos work because of a combination of gravity and rotation. By
first either dropping or throwing down the round part, you have
created the first "Yo." This yo is known as the gravitational
yo. The round part falls to the bottom because of gravity.
Now the yo-yo does not stop there, otherwise it would simply be
known as a yo or a ball on string. Because there was kinetic energy
and rotational force when you threw the round part down, this, combined
with the friction on the string would give the yo-yo a chance to
complete its second "Yo" which is characterized by the
climb back up.
Remember, there are two parts to this journey, the first yo and
the second yo. The second yo involves the climb back up the string
and into your hand. The yo-yo climbs back up the string with its
rotational energy declining on the climb back up and almost has
enough to make it into your hand.
The hostess company actually developed the first yo-yo, though
they never could get it to function correctly, so they ended up
covering it in chocolate, wrapping it in tin foil and renaming them