Rotating Chair with Dumbbells

A person seated on a rotating chair holds dumbbells with arms extended. As the person pulls the dumbbells inward, the chair spins faster, demonstrating conservation of angular momentum. Extending the arms again slows the rotation.

1. Place a sturdy chair with a ball-bearing axle on a flat surface.
2. Have a person sit in the chair while holding a dumbbell in each hand with arms fully extended.
3. Gently set the chair in rotation.
4. Ask the person to pull the dumbbells inward toward their body and observe the increase in spin rate.
5. Have the person extend their arms outward again to slow the rotation.

Angular Momentum Demo: Platform and Dumbbells - Physics Demos:

Dumbbells on Spinning Chair - utexascnsquest:

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

• 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.

• 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.

• 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.)