Roberto Carlos Impossible Soccer goal "no fluke" - say Physicists

In 1997, Brazilian soccer player Roberto Carlos scored on a free kick that first went right, then curved sharply to the left in what looked like a physics-defying fluke. We’ve finally discovered the physics equation that shows it was no fluke.

Physicists have explained one of football's most spectacular goals.

Abstract. We discuss the trajectory of a fast revolving solid ball moving in a fluid of comparable density. As the ball slows down owing to drag, its trajectory follows an exponential spiral as long as the rotation speed remains constant: at the characteristic distance \mathcal{L} where the ball speed is significantly affected by the drag, the bending of the trajectory increases, surprisingly. Later, the rotation speed decreases, which makes the ball follow a second kind of spiral, also described in the paper. Finally, the use of these highly curved trajectories is shown to be relevant to sports. For more information visit New Journal of Physics website.
 
Here’s the original “impossible” kicks:



via www.bbc.co.uk

Oil-based color pixels could let you watch videos on e-paper

By rapidly manipulating colored oil droplets stacked on top of each other, a new electrowetting (EW) technique could lead to the development of electronic paper displays that can produce high-resolution color video. Displays that use the EW effect could have several advantages over today’s e-readers and other portable flat panel displays, most of which are based on electrophoretic (EPh) technology.

Researchers have demonstrated a vertical stack approach for electrowetting displays that can produce high-resolution color video. Top: A diagram of the device structure. Bottom left: Photographs of the pixel array with all pixels off (a) and on (f); numbers indicate the voltage applied to each layer. Bottom right: Graph showing the switching speed of each color.

via www.physorg.com