Friction is the key to domino physics

Physics 15, 83

The main campaign for shogi perversion simulation brings new insights into the effects of friction.

fall down. A new simulation reveals the role of friction in the seemingly simple mechanism of domino collapse. (See the video below.)

Despite the obvious simplicity of defeating dominoes, physicists do not yet have a complete model of the phenomenon. However, the new numerical simulation goes one step further by solving the effects of two types of friction. One is between adjacent dominoes and the other is between each domino and the surface below it. [1].. Researchers have found that, in some cases, these two coefficients of friction play competing roles in determining the velocity of the domino cascade. They also found that one of the coefficients behaves like friction in granular systems such as sand piles and drug pills, and domino simulations could provide insight into other situations where friction is important. It suggests that there is.

YouTube video by engineer Destin Sandrin (his channel) Be smart every day) I urged David Cantor of the Polytechnique Montréal and Kajetan Wojtacki of the Polish Academy of Sciences in Warsaw to study dominoes. Sandrin recorded a series of domino collapse experiments using a high-speed camera and quickly discovered how complex the problem was. He determined that the falling domino waves would move slightly faster on the felt than on the slippery hardwood floor. He also saw some surprising anomalies, such as when a fallen domino train suddenly stopped.

Sandrin observed that the slippery surface could tilt the domino forward and slide it backwards, hitting the next domino slightly lower when compared to the high-friction felt domino. However, due to experimental limitations, he was unable to fully explain the effect of friction on wave velocity. Researchers have conducted experiments and simulations to develop the theory of domino collapse, but those who have systematically studied how domino surface friction, domino-domino friction, and domino spacing affect wave speed. There is no one. Cantor and Wojtacki ran simulations with full control over these parameters, hoping to better explain the observations.

D. Sandrin / Smarter Every Day

On slippery surfaces, Domino slides back when it falls forward. (Clip from Sandrin’s first domino video.)

D. Sandrin / Smarter Every Day

On a frictional surface, there is much less backsliding. (Clip from Sandrin’s first domino video.)

Cantor and Wojtacki discover from a comprehensive campaign of 1210 simulations, each containing 200 dominoes, that domino surface friction and domino domino friction play a competing role when the spacing is half the thickness of the domino. Did. The wavefront slows down as friction absorbs some energy from the waves of motion. Researchers believe that increasing friction with the underlying surface reduces the domino’s backslip, allowing each to hit the next person higher, resulting in faster waves and more effective impacts.

However, as the domino spacing increased (the team observed up to five times the domino thickness), surface friction had little effect on wave velocity. Cantor and Wojtacki believe that the wider the spacing, the more dominoes will fall and gain more kinetic energy before hitting adjacent dominoes. You can see that the stronger the impact, the less likely the domino will slide back, regardless of surface friction.

Cantor and Wojtacki also found that at intervals wider than three times the thickness of the domino, the waves are unstable, the surface is relatively slippery, and can stop spontaneously if the domino-domino friction is high. discovered. In this case, the backslide can cause the waves to stop due to the wide spacing. Dominoes can fall, but they can slide so far that they can’t reach their neighbors.

The pair also observed that the wavefront velocity did not change much when the domino-domino friction coefficient was increased by more than 0.4. Cantor and Wojtacki believe that the greater the friction, the less the dominoes will slide against each other. Therefore, in the end, the amount of friction is not important. Researchers write that studies of the effect of friction on the steep slopes of the stable mountain sides of sand or other granular materials showed a similar “saturation” effect at values ​​of about 0.4. Therefore, they speculate that a universal phenomenon may be involved.

Peking University’s Kaishan Liu says that domino-like behavior is ubiquitous and can be seen in phenomena ranging from nano-friction and molecular collisions to earthquakes and economic activity. “It was one of the basic scientific problems to characterize the relationship between the macroscopic movements of such systems and the microscopic mechanisms,” he says.

Liu believes Cantor and Woitacchi’s work is “important for understanding the relationship between the global behavior of domino systems and physical parameters,” but states that the problem has not yet been resolved. .. “There is still a lot of work to be done to clarify the physical mechanism.”

– Katy McCormick

Katie McCormick is a freelance science writer based in Seattle, Washington.


  1. D. Cantor and K. Wojtacki, “Effects of Friction and Spacing on Cooperative Behavior of Domino Collapse” Pastor of Physics applied 17 17064021 (2022).

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