It’s all about angular momentum — a quantity that stays conserved (unchanged) if there’s no external force. Imagine a figure skater spinning: 🌀 Arms extended = slower spin 🌀 Arms pulled in = faster spin Why? Because when the skater pulls their arms in, they reduce their moment of inertia (how mass is spread out from the center). But since angular momentum must stay the same, the body compensates by spinning faster. No extra force needed — just smarter movement. This same principle explains how

DYNAMICS, Example 15.7.2 Angular Momentum