Presets
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Carousel and puck
Launch the puck, then compare the two views. A faster spin bends the path more.
Model checks
The science
Two descriptions of one motion
A frictionless puck feels no horizontal force, so from the ground it moves in a straight line at constant speed. The platform turns underneath it, so from the platform the same path curves. To keep Newton's laws working there you add two fictitious accelerations: centrifugal Ω2 r (outward) and Coriolis -2 Ω × v (sideways, at right angles to the motion).
Launch
The launcher is fixed on the platform, so the puck also carries the deck's own velocity: vin = vrel + Ω × r0. For small spin the sideways drift is about Ω v t2, and the Rossby number Ro = v / (2 Ω L) tells whether rotation (Ro below 1) or inertia dominates.
Earth
On Earth the local vertical part of the planet's spin gives f = 2 ΩE sin(latitude), at most 1.46×10-4 s-1. A carousel turning once every 8 s is hundreds of times faster, which is why the effect is obvious here and invisible in a sink.
Honest simplifications
- The puck is a point mass with no friction or drag, gravity is carried by the deck, and the deck turns at a constant rate; a rolling ball would behave a little differently because of its own spin.
- After leaving the deck the puck just keeps its straight line. The deck picture is a Blender render of the 3D page's carousel model.
What to try
- Press Launch with Standing still, then with Gentle carousel, and compare the two views.
- Press Aim at the bumper for me and watch the puck curve onto the target.
- Reverse the spin and see the drift change sides.
- Raise the launch speed in the third graph: the faster puck is bent less (Rossby number grows).