Every golfer knows the heartbreak of a lip out — when the ball seems destined for the hole, only to cruelly circle the rim and spin back onto the green. Now, scientists at the University of Bristol have revealed the precise mechanics behind this frustrating golfing phenomenon.
Published in Royal Society Open Science, the new research, led by Emeritus Professor John Hogan from Bristol’s School of Engineering Mathematics and Technology, delves into the science of what makes a putt stay out when it looks certain to drop.
Professor Hogan, who has dubbed these near misses as ‘the golf balls of death’, says the motion is strikingly similar to the ‘wall of death’ stunt performed by motorcycle riders inside a circular arena. “We considered the motion from the point of view of mechanics,” he explained. “We showed analytically there are two distinct types of lip out: the rim lip out, where the centre of mass of the golf ball does not fall below the level of the green, and the hole lip out, where it does.”
At the core of both events lies what Professor Hogan describes as a ‘degenerate saddle equilibrium’ — the delicate balance point where the ball teeters on the edge of the hole. It’s neither safely on the green nor falling into the cup, but hovering on the very brink.
In the first case – the ‘rim’ lip out – the ball rotates around the top edge of the hole at a constant angle and speed. Tiny factors such as a puff of wind, a grain of sand, or a touch of unwanted spin can tip the ball either back onto the green or down into the cup.
By contrast, the ‘hole’ lip out occurs only under a narrow set of conditions. “Here the golf ball falls into the hole, where it undergoes a pendulum-like motion, as it rolls around the wall of the hole,” said Hogan. “Its potential energy is converted into spin, and then, provided the golf ball does not touch the bottom of the hole, it can return to the rim and back onto the green again.”
So what can golfers do to avoid suffering a lip out? While there’s no easy fix, Hogan’s research does offer a scientific clue.
“My golfing friends tell me that lip outs occur when you hit the ball too hard,” he noted. “Our research has shown that you need to aim as close to the centre of the hole as possible, and to arrive at the rim of the hole with little speed. That combination means that the small amount of momentum the ball does have is just enough to tip the ball into the hole, and not enough to carry it around the rim and back onto the green.”