No player can return this killer shot. Physics explains how it works

It’s the shot every squash player dreads and dreams of.

In the sport, players take turns hitting a squishy ball off four walls, trying to return it before it bounces twice. But when a perfect “nick shot” is executed, the ball strikes a sweet spot between the wall and floor. Instead of bouncing, it rolls back flat on the ground — making it impossible for the opponent to return.

The physics behind this killer shot all comes down to height, timing and the signature squashiness of the ball, researchers reported in May in the Proceedings of the National Academy of Sciences.

“What’s most impressive about professional athletes is that they know all of these ideas in an empirical way,” says Roberto Zenit, an engineer at Brown University. “You need to have a certain set of conditions to hit the nick, and you have a fraction of a second to decide.”

To find out how nick shots work, Zenit and his colleagues used a pressurized air cannon to lob three different kinds of squash balls. After varying launch angles and speeds to simulate real-world play and recording each shot with high-speed cameras, they discovered that nick shots occur only under two key conditions.

First, the ball must strike the wall within a narrow height range, about 2.5 to 3 centimeters or roughly an inch above the floor. At this height, the ball compresses and starts to roll downward along the vertical surface. Friction keeps it flush with the wall as it deforms and its center of mass shifts lower.

Second, the time the ball spends pressed into the wall must exceed the time it spends rolling down it. This imbalance is crucial: when the rolling ball’s bottom edge touches the floor, a second point of contact is introduced. The wall pushes one way, and the floor the opposite. The result is a mechanical deadlock that cancels out both the ball’s spin and vertical motion.

If the ball were rigid, like a billiard ball, it would end up stuck in the corner, Zenit says. But squash balls are elastic. Even as the ball is pinned at two contact points, it’s still pressed into the wall, accumulating stored energy. As the ball fully decompresses, that energy is released almost entirely as horizontal motion — sending the ball skimming out of the corner with virtually zero vertical lift.

These dynamics proved consistent across all the ball types, temperatures and speeds the researchers tested. “Their experiments are really impressive and quite exhaustive,” says physicist Philippe Brunet of Paris Cité University — though based on his own experiments, he suspects that nick shots could be even rarer than the new study suggests.

So, how do players maximize their odds of a nick shot? A warm ball, a strong hit and a fully extended arm can help, Zenit says. But theory doesn’t always translate to experience, he says. “The sad part of this story is that I don’t think my squash skills have improved much, even if I understand how this shot behaves mechanically.”