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Figure Skater Angular Momentum Conservation

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About This MicroSim

This simulation demonstrates the conservation of angular momentum. When a spinning figure skater pulls their arms in, they spin faster - and this isn't magic, it's physics!

The Physics

Angular momentum is conserved: L = Iω = constant

When arms are pulled in: - I decreases (mass moves closer to rotation axis) - ω must increase to keep L constant - The skater spins faster!

When arms extend: - I increases (mass moves farther from axis) - ω must decrease to keep L constant - The skater slows down!

Controls

  • Arm Extension Slider: Move arms in (0%) or out (100%)
  • Initial ω Slider: Set the starting angular velocity
  • Show kinetic energy: See how KE changes (it's not conserved!)
  • Reset: Return to initial state

Key Insight

Notice that while angular momentum stays constant, kinetic energy changes! When the skater pulls their arms in, they do work against centripetal force, adding energy to the system.

Lesson Plan

Discussion Questions

  1. Where does the extra kinetic energy come from when arms are pulled in?
  2. Why doesn't conservation of energy apply here?
  3. Calculate: If I drops from 5 to 2 kg·m², by what factor does ω increase?