this is pretty awesome…everyone remember this famous goal by roberto carlos leading up to the 1998 world cup?
well, scientists have taken a look at the trajectory and come up with an equation that actually explains the physics of the trajectory of that shot:
Using tiny plastic balls and a slingshot, the researchers varied the velocity and spin of balls travelling through water to trace different trajectories.
This allowed them to study the aerodynamics of the balls without having to account for gravity and perform their experiments in a small tank instead of a large field.
While the study quickly confirmed the long-known ‘Magnus effect’, which gives a spinning ball a curved trajectory, it also revealed fresh insight for spinning balls that are shot over a distance equivalent to Carlos’ free kick.
The researchers said the friction exerted on a ball by its surrounding atmosphere slows it down enough for the spin to take on a greater role in directing the ball’s trajectory.
Prof Clanet said: ‘If he had not hit it so hard then gravity would have stopped it from taking the path it did. And he would have not have been able to curve it in such a way if he had been nearer the goal. That is why you never see penalty kicks swerve.’
It all comes down to the fact that, when a sphere spins, its trajectory is a spiral. Usually, gravity and the relatively short distance the ball travels cover up this spiral trajectory, but Carlos was a mere 115 feet away and kicked the ball hard enough to reveal its true spiral-like path. As you can see in the diagram above, the ball would have kept spiraling if gravity (and the netting) hadn’t gotten in the way.
sources: 1. Impossible soccer kick leads to new physics equation
2. Greatest free-kick was no fluke: Roberto Carlos’ 1997 ‘freak’ goal explained by scientists
