I keep getting “Angular momentum” questions wrong in Rotational Motion. What's the trap?
forgetting that pulling mass inward lowers I and therefore speeds up rotation.
The usual trap: forgetting that pulling mass inward lowers I and therefore speeds up rotation. How to avoid it: a skater spins faster by pulling their arms in — conservation of L. Go back to the definition — L = Iω, conserved when the net external torque is zero.
Key point
Angular momentum
Common mistake
forgetting that pulling mass inward lowers I and therefore speeds up rotation.
Memory tip
a skater spins faster by pulling their arms in — conservation of L.
Tap to watch or see it right here — the app stays open (it only opens a quick search if nothing embeddable is found).