======Rotating Chair with Dumbbells======


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**Materials: **{{$demo.materials_description}}\\
**Difficulty: **{{$demo.difficulty_description}}\\
**Safety: **{{$demo.safety_description}}\\
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**Alternative titles:** Conservation of Angular Momentum with Dumbbells
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====Summary====                   
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====Procedure====  
  - Place a sturdy chair with a ball-bearing axle on a flat surface.  
  - Have a person sit in the chair while holding a dumbbell in each hand with arms fully extended.  
  - Gently set the chair in rotation.  
  - Ask the person to pull the dumbbells inward toward their body and observe the increase in spin rate.  
  - Have the person extend their arms outward again to slow the rotation.



====Links==== 
Angular Momentum Demo: Platform and Dumbbells - Physics Demos: 
{{youtube>fwAjPOR28J0?}}\\

Dumbbells on Spinning Chair - utexascnsquest: 
{{youtube>uJObaTw1PAU?}}\\

📄 Rotating chair with dumbbells or weighted bicycle wheel. - Physics @ Berkeley: [[https://berkeleyphysicsdemos.net/node/73]]\\


====Variations====
  * Use heavier or lighter dumbbells to compare how mass affects the effect.  
  * Try different arm positions (partially extended, fully extended) to see how rotation speed changes.  
  * Two participants can compare their experiences if one is holding heavier weights than the other.



====Safety Precautions====
  * Ensure the chair is on a stable surface and cannot roll or tip.  
  * Use a sturdy chair with proper bearings to prevent sudden stops or falls.  
  * Weights should be secure and not too heavy for the person holding them.  
  * A supervisor should stand nearby in case assistance is needed.




====Questions to Consider====
  * Why does pulling the dumbbells inward cause the chair to spin faster? (Because reducing rotational inertia increases angular velocity while conserving angular momentum.)  
  * What happens to the rotation when the dumbbells are extended outward? (The chair slows as rotational inertia increases.)  
  * Where else can you see conservation of angular momentum in action? (Examples include figure skaters pulling in their arms or divers tucking into a spin.)