Simone Biles has been taking the gymnastics world by storm since 2013. As part of the legendary gold-winning “Final Five” in the 2016 summer games, she also won three individual gold medals there (all-around, vault, and floor exercise) and a bronze in the balance beam. These weren’t her first medals and victories, and they weren’t her last ones.
Last week, she nailed a triple-double in her floor exercise (the first woman to do so), and she also scored a double-double dismount from the balance beam (the first human to do so). The incredible slow-motion video above (from R.P.A. TV), shows her artistry and her control. I knew those terms better from skating than from gymnastics. Here’s what they mean.
In a double-double dismount, the athlete completes a double twist and double somersault in one move coming off the beam. In a floor triple-double, the gymnast rotates around the axis of her hips twice while at the same time rotating about an axis of her height three times. If you care (I kind of do), Rhett Allain at Wired sorts out the physics of the triple-double. I’ll spare you the equations, which you can find at the link.
Once a human leaves the floor, there is essentially only one force acting on him or her—the gravitational force. This is a downward-pulling force that depends on the local gravitational field (g = 9.8 Newtons per kilogram) and the mass of the human (or whatever object). This constant downward force causes a person to accelerate downward. But because both the force and the acceleration depend on mass, the mass cancels out. All free-falling objects on the surface of the Earth have the same acceleration of -9.8 m/s2.
The other great thing about the gravitational force is that it only acts in the vertical direction. This means that there are no net forces in the horizontal direction. With no net force, there is no CHANGE in velocity. Once she’s in the air, Simone’s center of mass will move along with a constant speed—with the same horizontal velocity at which she was running before the jump.
But in the vertical direction, she launches upward with some vertical velocity. This velocity decreases as she travels up until it reaches zero at the highest point of the jump. At that point, she starts moving down and increasing in speed until she returns to the floor.
Of course, no athlete is thinking about gravitational forces or equations while contorting her body through the air; that all happens in the training and the body knowledge.
Biles is 22, which while it may sound young to many readers, is quite old for a female gymnast. And she’s clearly at the top of her game. It’s time to stop just acknowledging that she’s the world’s greatest gymnast: she’s one of the world’s greatest athletes. What will she do in 2020?