A yo-yo moves up and down through a combination of physics principles and the design of the yo-yo itself. Here’s a simplified explanation of how it works:

Starting Position: When you throw a yo-yo down, you give it an initial spin and a downward force. This is usually done by flicking your wrist while holding the yo-yo.

Spinning and Gravity: As the yo-yo descends, it spins rapidly. The spinning motion creates angular momentum, which helps the yo-yo maintain its stability and resist changes in direction. Gravity pulls the yo-yo downward, but the spinning motion keeps it stable on the string.

String Tension and Return: The string is wound around the axle (the central rod of the yo-yo). When the yo-yo reaches the end of its downward path, the tension in the string causes it to start climbing back up. This is because the spinning yo-yo winds the string around the axle, pulling itself upward.

Rewind and Repeat: As the yo-yo ascends, the string unwinds from around the axle, and the yo-yo continues to spin. Once it reaches the top, the spinning motion helps it stay centered on the string. You can then throw it down again to repeat the motion.

The key elements are the yo-yo’s spinning motion (which helps it stay stable and resist wobbling) and the string’s tension (which causes the yo-yo to climb back up).