Plus Blog

January 25, 2006
Wednesday, January 25, 2006

Football physics (25/01/2006)

Nicholas Linthorne and David Everett from the University of Brunel, UK, have worked out the optimum angle for a footballer to launch a throw-in — it's 30 degrees to the horizontal, 15 degrees less than textbooks normally state. The two filmed a player throwing the ball at angles between 10 and 60 degrees and then used biomechanical software to measure velocity and angle in each case. Using the equations that describe the flight of a spherical object, they calculated the optimum launch angle to be 30 degrees. Thrown at this angle, the ball has the best chance to fly all the way to the penalty area, giving other players a great opportunity to score. And it goes even further if it's launched with a backspin at an even lower angle.

The same methods can be used for any other sport involving the throwing of a ball. Next, Linthorne will calculate the optimum angle at which to take a goal kick. To find out more, read their paper Release angle for attaining maximum distance in the soccer throw-in, or look at Nicholas Linthorne's homepage.

posted by Plus @ 2:10 PM

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January 16, 2006
Monday, January 16, 2006

US law is Euclidean (16/01/2006)

This is what one James Robbins found out when he stood trial for drug dealing in New York last year. US law decrees that selling drugs within 1000 feet of a school carries extra penalties. Unfortunately, Robbins had been caught within that radius, so his lawyer decided simply to change the metric. He argued that the Euclidean metric, which measures distances along straight lines between points, should be replaced by a "Taxicab metric", which measures distances along the roads a taxi, or a pedestrian, has to take to get from point to point. After all, students from the school in question are unlikely to walk through brick walls. According to this new metric, Robbins was 1254 feet away from the school: 764 feet north along Eighth Avenue and 490 feet west along 43rd Street. Alas, judge and jury were unimpressed by this mathematical trickery and Robbins lost.

posted by Plus @ 2:09 PM

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January 16, 2006
Monday, January 16, 2006

Einstein is proved right (16/01/2006)

Unlike human celebrities, equations have to prove their merit to be famous. Now Einstein's e=mc2 has done just that. An experiment conducted by US researchers from the National Institute of Standards and Technology and the Massachusetts Institute of Technology, showed that e differs from mc2 by at most 0.0000004, proving beyond doubt that the equation is indeed correct.

The equation, which just celebrated its 100th birthday, is part of Einstein's special theory of relativity and relates energy (e) to mass (m) and the speed of light (c). The recent experiment is the most precise and direct test of the equation ever conducted. Its results were published in the journal Nature. You can find out more about the experiment in this news release. To see special relativity in action, read Plus article What's so special about special relativity?. Another Plus article, Spinning in space, describes how the general theory of relativity is put to the test.

posted by Plus @ 1:20 PM

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