Ten steel balls roll between the inner and outer rings within a yoyoâ€™s shell. They work together to reduce friction, allowing the yoyo to keep spinning at the bottom of the string for over 10 minutes.
MACHINES: HOW THEY WORK
Thursdays 10/9c on Science
Subscribe to Science Channel:
Check out SCI2 for infinitely awesome science videos. Every day.
Download the TestTube app: