After witnessing her first competition as a kid, Gallegos found a group called the Mexican Yo-Yo Association. It offered free yo-yo lessons to local kids and set up workshops that Gallegos began to attend. There, she says, “I started to learn basic tricks like The Sleeper.” This simple maneuver, where the yo-yo keeps spinning at the end of its string, is the first step in any professional routine (see Tricky Techniques).
To make a yo-yo “sleep,” Gallegos throws it toward the ground. As the yo-yo leaves her hand, it has stored potential energy because of its elevated position, explains Maria Holland. She’s a mechanical engineer at the University of Notre Dame in Indiana. The force of gravity then pulls the yo-yo downward, turning potential energy into kinetic energy, or energy of motion. As the yo-yo falls, the string wrapped around its central axle unwinds, causing the yo-yo to rotate. It continues to spin when it reaches the bottom of the string.