From: veritasium
Ben Conde, a renowned yoyoer, demonstrates complex yoyo tricks, including techniques where the string is not connected to the yoyo [00:00:25]. Understanding how these intricate maneuvers are possible involves several principles of physics.
Basic Yoyo Mechanics
When a yoyo is released, it unspools as it falls, converting its initial gravitational potential energy into kinetic energy and rotational energy [00:01:08]. Yoyos are designed to spin exceptionally fast, often reaching speeds of around 6,000 revolutions per minute (RPM) [00:01:16]. This speed is comparable to that of most car engines [00:01:24].
Gyroscopic Stability
The rapid spin rate of a yoyo is crucial because it provides gyroscopic stability [00:01:28]. This stability ensures that the yoyo’s axis of rotation is maintained, even when subjected to minor disturbances like a breeze [00:01:32]. Due to its significant angular momentum, the yoyo continues to spin in the same direction [00:01:36].
Retrieving the Yoyo
To get the yoyo to return, a specific action is performed:
- String Binding: When Ben tugs the string, he pulls it from one side of the yoyo to the other [00:01:42]. As the yoyo continues to spin, this action binds the string to the spool, causing the yoyo to roll back up the string [00:01:46]. The exact moment of this binding can be observed, which prevents the yoyo from unravelling further and falling [00:01:50].
Stringless Yoyo Techniques
For stringless yoyo techniques, the initial release is key:
- Release: The yoyo is thrown outward and upward without a pull back [00:02:09]. This allows the yoyo to completely unspool and continue spinning at its high rate of rotation, now detached from the string [00:02:11].
- Catching: To catch a freely spinning yoyo with just a string, it relies on friction [00:02:20].
- Friction Pads: Modern yoyos contain friction pads, often made of silicone, inside a small gap [00:02:27]. When the string is lodged into this gap, it catches on these pads, and the yoyo begins to roll back up the string [00:02:38].
- Belt Friction Equation: Even without specific friction pads, wrapping the string around the axle creates significant friction [00:02:45]. This principle is similar to how ropes wrapped around bollards can hold large ships [00:02:48]. The amount of tension a coiled rope or string can hold is described by the belt friction equation [00:02:56]. This equation demonstrates that the force the string can exert on the yoyo increases exponentially with the angle the string makes around the axle [00:03:01]. Even a few turns around the yoyo’s axle can generate enough friction for Ben to pull it back into his hand [00:03:05].
Credits
This episode of Veritasium features slow-motion shots filmed by Darren Dyke [00:04:29] and demonstrations by Ben Conde [00:04:36].