Boone (dpa) – Pub game lovers beware: Physicists have figured out why beer mats don’t fly straight ahead. In order to clarify this question, which arose during a bar evening, researchers at the University of Bonn built a throwing machine and photographed the flight behavior of circular coasters with a high-speed camera.
The result of the analysis: If a beer mat lying next to the target table falls, it is not necessarily because of the alcohol level. Instead, the reason is “the interaction between gravity, buoyancy and the conservation of angular momentum,” as the team reports under “Beer mugs are bad Frisbee bowls” in the European Physical Journal Plus. After 0.45 seconds at the latest, the beer mat inevitably begins to drift away.
Floating causes the cover to tilt to the side
Reason: Shortly after throwing, the cover is tilted back slightly due to gravity, so that the angle of attack resembles a landing plane. This tilt creates buoyancy in the front third of the airflow. Since round cardboard is usually rotated when thrown, similar to a Frisbee, it does not tip over, but the buoyancy allows it to drift to the side. At the same time it straightens, then quickly loses its height and falls to the ground.
The good news: With the right technology, almost any beer can be tossed with precision. First author Johann Ostmeyer advises, “If you really want to throw far and accurately, you should shoot the cap straight and put it back.”
The physicists warn of injuries: “Our sincere apologies to everyone who has injured a beer rug, whether it was through inaccurate aiming or the fact that we urged others to do silly experiments.”
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