Balls behaving badly

It may seem like I have balls on the brain if my last couple of posts are any indication. Balls are such a big part of sport and Sports Engineers are fascinated by the way they behave as they bounce on the ground and fly through the air.

I’ve seen two amazing videos recently which exhibit the way in which balls can still baffle us.

Rugby, the penalty of wind

The video below shows a Rugby player taking a penalty in what the Irish tourist board might describe as ‘a slight breeze’. Be sure to watch from all angles to get a good idea of what’s going on.

The back-spin naturally added to a rugby ball from a penalty kick generates lift which increases the distance travelled. The gale force wind in this case greatly increases the magnitude of the lift so that the ball seems to float in the air. Combine this with the huge drag forces and the ball nearly ends up back where it was kicked from!

Tennis, the ultimate drop shot

A colleague in the ITF showed me this video, and many of you may have seen it already. I’ve included a version with a Discovery channel commentary for a little more insight.

The ITF have done a massive amount of work on benchmarking surface behaviour, the bounce and spin of a playing surface can greatly affect the nature of the game. This video just goes to show how many factors there are governing the seemingly simple mechanism of a bounce. In this case it seems that a bubble in the court’s surface is absorbing almost all of the kinetic energy of the ball, stopping it dead.

As busy as we are at the Centre for Sports Engineering Research, we’ll try and post up interesting and exciting sports engineering videos as we come across them. You never know we may even get round to making some of our own in time.

Simon Choppin

About wiredchop

Simon Choppin Simon’s sports engineering career began at the age of six when he loosened the wheels of his skateboard in order to make it go faster. While the experiment was chalked up as his first failure, his resulting dimpled skull has provided an aerodynamic advantage in more recent sporting pursuits. Academically, Simon completed a degree in Mechanical Engineering with Mathematics at Nottingham University before joining the Sports Engineering Research Group at Sheffield to start his PhD. His main interests include work with high speed video, mathematical modelling of various sorts and experimental work involving machines with big buttons. As a sportsman, Simon has an unfortunate lack of talent for anything requiring skill, tactical awareness or the ability to learn from mistakes. He does however seem to posess the ability to move his legs around for a long time until other people get tired, for this reason you’re most likely to see him on a bike of some sort or running up a hill in offensively small shorts. Simon was fortunate enough to have a stint at the Guardian newspaper as part of the BSA’s media fellowship, which gave him the idea for this blog. Other than this, his writing experience includes his PhD thesis and various postcards to his Mum.

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