Labs / Physics
Spinning Skater
Give the skater a spin, then slide the arms in toward the body and back out. Because angular momentum L = I × ω is conserved, shrinking the moment of inertia I makes the spin rate ω shoot up — no push required. Add weights to the hands to make the effect even stronger.
I 0.00 kg·m²ω 0.00 rad/sL 0.00 kg·m²/s
What to try
- Pull the arms all the way in. Does the spin speed up or slow down, and by how much?
- Watch the L readout as you move the arm slider. Why does it stay put while ω changes?
- Load 5 kg into each hand and extend the arms. What happens to the spin rate now?
- With weights out, tuck the arms in fast. Can you make the skater spin faster than any push you gave it?
- If the moment of inertia doubles, what has to happen to ω to keep L the same?