An anonymous reader writes "What makes soccer star Christiano Ronaldo’s “knuckleball” shot so unpredictable and difficult to stop? A “knuckleball” in soccer refers to a ball kicked at very low spin, which results in a zigzag trajectory. Along its straight path, the ball deviates laterally by roughly the diameter of a ball (0.2 m). The deviation direction appears to be unpredictable, which is extremely frustrating for goalkeepers attempting to block it.
The research team demonstrated that – contrary to popular belief – the “knuckle effect” isn’t a result of deformations at the site of foot impact or ball seams."
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