The Tip-Top Demonstration (with a Rotating Field)
A tip-top is a round spinning top with its center of mass shifted away from its geometric center (often by having a small stem or button on top). When you spin it fast enough on a smooth surface, something surprising happens:
Instead of spinning calmly like an ordinary top,
The tip-top flips over, raising its heavy brass body upward and balancing on the very tip of its stem.
This is called inversion.
Why it happens
The spinning motion creates gyroscopic stability, but friction at the contact point with the surface exerts a torque.
Because the center of mass is off-center, this torque causes the top’s axis to slowly tilt.
Instead of falling, the top’s energy redistributes, and it climbs upward, inverting itself so that the heavy side is now above.
Angular momentum is conserved, but its orientation shifts — a counterintuitive effect!
Using a Rotating Field
In a demonstration with a rotating magnetic or mechanical field under the brass tip-top:
The external field can “pump” angular momentum into the top.
This acts like a parametric driver, sustaining the spin and even controlling the direction or speed of inversion.
Viewers see the brass top suddenly flip onto its stem and continue spinning — a beautiful, counterintuitive mix of symmetry, friction, and dynamics.
✨ In short: A brass tip-top placed in a rotating field spins, wobbles, and then astonishingly flips itself upside down, balancing on its stem. The trick lies in hidden asymmetry, torque, and conservation of angular momentum.