The high-speed physics of how bobsled, luge and skeleton send humans hurtling faster than a car on the highway
Speed alone may be the factor that draws many sports fans to the bobsled, luge and skeleton events at this year’s Beijing Winter Olympics. But beneath the thrilling descents of the winding, ice-covered track, a myriad of concepts from physics are at play. It is how the athletes react to the physics that ultimately determines the fastest runs from the rest of the pack.
I study the physics of sports. Much of the excitement of a luge run is easy to miss – the athletes’ movements are often too small to notice as they fly by looking like nothing more than a blur on your television. It would be easy to assume that the competitors are simply falling or sliding down a track at the whim of gravity. But that thought merely scratches the surface of all the subtle physics that go into a gold-medal-winning performance.
Gravity and energy
Gravity is what powers the sleds down the ice-covered tracks in bobsled, luge and skeleton events. The big-picture physics is simple – start at some height and then fall to a lower height, letting gravity accelerate athletes to speeds approaching 90 mph (145 kph).
Riders in the sledding events reach their fast speeds because of the conversion of gravitational potential energy into kinetic energy. Gravitational potential energy represents stored energy and increases as an object is raised farther from Earth’s surface. The potential energy is converted to another form of energy once the object starts falling. Kinetic energy is the energy of motion. The reason a flying baseball will shatter the glass if it hits a window is that the ball transfers its kinetic energy to the glass. Both gravitational potential energy and kinetic energy increase as weight increases, meaning there is more energy in a four-person bobsled team than there is in a one-person luge or skeleton for a given speed.
Racers are dealing with a lot of kinetic energy and strong forces. When athletes enter a turn at 80 mph (129 kph) they experience accelerations that can reach five times that of normal gravitational acceleration. Though bobsled, luge and skeleton may look easy, in reality they are anything but.