Euler's Disk

A striking demonstration of angular momentum and energy conservation Euler’s Disk is a captivating tabletop demonstration that sparks curiosity, debate, and deep thinking about energy conservation and angular momentum. Simple to use yet rich in complexity, this heavy metal disk spinning on a smooth concave mirror creates an unforgettable visual: the disk rotates and rolls for an astonishingly long time—then suddenly speeds up as it nears the surface. It’s a deceptively simple setup that invites big questions and lively classroom discussion. Why Teachers Love Euler’s Disk Instant engagement: The dramatic motion naturally draws students in and prompts questions. Big ideas, simple setup: Demonstrates conservation of energy and angular momentum with a single twist. Discussion-driven learning: Encourages prediction, explanation, and debate across multiple levels of understanding. Durable and classroom-ready: Heavy metal disk and a 9-inch diameter mirror built for repeated use.