======Turntable Paradox======


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**Materials: **{{$demo.materials_description}}\\
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**Safety: **{{$demo.safety_description}}\\
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**Alternative titles:** Billiard Ball Turntable Paradox
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====Summary====                   
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====Procedure====  
  - Place a rotating turntable on a stable base with its axis vertical.  
  - Gently place a solid spherical ball near the center of the turntable surface.  
  - Rotate the turntable at a steady speed.  
  - Observe the motion of the ball as it rolls across the surface.  
  - Note how the ball follows a spiral path instead of sliding straight off.  
  - Compare the ball’s angular speed with that of the turntable.



====Links==== 
The Turntable Paradox - Steve Mould: 
{{youtube>3oM7hX3UUEU?}}\\

📄 The Turntable Paradox - C_R 3442: [[https://www.mapleprimes.com/posts/224435-The-Turntable-Paradox]]\\


====Variations====
  * Try different sizes of balls.  
  * Use balls with different masses but similar radii.  
  * Vary the rotation speed of the turntable.  
  * Compare the behavior of a hollow sphere versus a solid sphere.  
  * Change the friction of the surface (rough vs smooth).



====Safety Precautions====
  * Ensure the turntable is stable and securely mounted.  
  * Keep hands and loose objects away from the spinning edge. 
  * Avoid high rotation speeds that may launch the ball dangerously.




====Questions to Consider====
  * Why doesn’t the ball immediately slide off the turntable? (Because rolling friction and rotational inertia redirect its motion into a spiral path.)  
  * What is the relationship between the ball’s orbital angular speed and the turntable’s angular speed? (For a solid sphere, the ball’s orbital angular speed is 2/7 that of the turntable.)  
  * How do mass and radius affect the motion? (They change the ball’s moment of inertia, influencing how easily it spins.)
  * How does surface friction alter the path?  
  * Will the ball eventually leave the turntable? (Yes, over time frictional effects and imperfect rolling may cause it to drift outward.)