Study of curling mechanism by precision kinematic measurements of curling stone's motion

TL;DR

This paper investigates the physical mechanism behind the curling of stones in the sport, using precise kinematic measurements to identify asymmetric friction and angular momentum transfer as key factors.

Contribution

It provides experimental evidence that asymmetric friction and swinging around slow-side friction points are the main causes of curling, resolving a century-long debate.

Findings

Asymmetric friction depends on velocity.

Swinging around slow-side friction points causes curling.

New angular momentum transfer phenomena were observed.

Abstract

Why do curling stones curl? That is a question physicists are often asked, yet no answer has been established. Stones rotating clockwise curl right, contrary to our naive expectations. After a century of debate between contradicting hypotheses, this paper provides the answer based on experimental evidence. A digital image analysis technique was used to perform precision kinematic measurements of a curling stone's motion to identify the curling mechanism. We observed a significant left-right asymmetric friction due to velocity dependence on the friction constant. Combined with the discrete point-like nature of the friction between ice and stone, swinging around slow-side friction points has been concluded as the dominant origin of the curling. Many new angular momentum transfer phenomena have been found, supporting this conclusion.