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It’s purely physics

Red Bull X-Fighters 2011 - Dubai - Maddison © J. Mitter -

Red Bull X-Fighters – it’s pure action. The best motocross freestylers fly through the air up to 30 meters and beyond in front of frenzied crowds in packed arenas. The crowds gasp in awe whenever the aces like Nate Adams or Australia’s Robbie Maddison rotate their bikes in mid-flight while some 15 meters above the ground. They are – seemingly - defying the laws of physics.

Back in the 17th century, a young man named Isaac Newton was sitting in the backyard with his parents when a falling apple hit him on the head. That made him curious and that is how he stumbled upon gravity. He described the laws of universal gravitation and they are still valid today. Apples do fall from trees.

Yet the bikes ridden by the Red Bull X-Riders climb to heights of up to 15 meters – defying gravity. But mass bodies attract each other, according to Newton. In other words, the large mass -- the earth -- pulls the small mass – the bike and rider – back towards it. And that’s putting it mildly. It is not unusual for the heroes of the air to land on the ground of hard realities with a force equal to three times their own weight. In best-case scenarios they return to earth under control.

It’s all only physics. Take Robbie Maddison, for instance. In 2007 the Australian landed his freestyle motocross bike safely in the sand after leaping a then-world record distance of 98.3 meters. From a purely physics point of view, he could have jumped even further. Because the theoretical jump distance can be calculated from the mass of the bike plus the rider. Take the speed at the take-off point and the angle of the jump. But at the same time the flight-speed can be affected by the air density. Because there was a strong headwind blowing against Maddison, his jump was several meters shorter than what it might have been. Physicists have calculated that, without headwind, a jump of nearly 125 meters might have been possible.

Starting on Friday the centrifugal forces will once again be back on center stage at the opening of the Red Bull X-Fighters 2011 season in Dubai. The world’s 12 best freestyle motocross athletes will be taking off in front of 15,000 fans at the city’s grand Jumeirah Beach.

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