A man effortlessly lifts a 42-pound weight at the end of a long rod over his head. It seems like it's floating! What is this sorcery? Is this guy a wizard? Perhaps he has discovered an anti-gravity device to make Back to the Future skateboards? Actually, it's just good old physics in action.
First watch the demonstration by Veritasium's Derek Muller:
The phenomenon that makes this seemingly magical act possible is called torque-induced precession—also known as gyroscopic precession:
Torque-induced precession is the phenomenon in which the axis of a spinning object (e.g., a part of a gyroscope) "wobbles" when a torque is applied to it, which causes a distribution of force around the acted axis. The phenomenon is commonly seen in a spinning toy top, but all rotating objects can undergo precession. If the speed of the rotation and the magnitude of the torque are constant, the axis will describe a cone, its movement at any instant being at right angles to the direction of the torque. In the case of a toy top, its weight is acting downwards from its centre of mass and the normal force (reaction) of the ground pushing up on it at the point of contact with the support constitute two opposite and equal forces producing a torque.
The phenomenon doesn't make the weight lighter, although it will feel lighter to person lifting it. Still not clear about how it works? Here's the video that explains it all in detail:
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