The Physics of Gymnastics

Torque

THE TORQUE: When a gymnast performs a somersault or twist on the floor, she usually does a round off or back handspring to give herself more speed to initiate them. These lever like movements are defined as the perpendicular distance from the axis of rotation to a line along which the force acts. The amount of force produced plus the lever is called the torque. The greater the torque, the greater the change or number of somersaults a gymnast will be able to perform in one series. Therefore, the torque plays the role of rotational motion in somersaults and twists.

Somersaults

1.SOMERSAULT DUE TO HORIZONTAL FORCES- This is the most common way to initiate a somersault, by applying horizontal forces to the feet. Gymnasts "throw" with their upper bodies. "Throwing the arms and head backward and up involves a rotation of the gymnast's arms which also contains angular momentum which is conserved.

2. SOMERSAULT DUE TO VERTICAL FORCES- The gymnast can perform a somersault without any "throw" from the spring floor,even if only vertical forces act on her feet. In this case, the gymnasts center mass cannot be directly above her feet, this is because she "leans" either forward or backward that the vertical forces produce a torque.

3. TORQUE-FREE SOMERSAULT- This means that a gymnast can achieve a limited amount of body rotation without any torque whatsoever. A gymnast can do this be keeping her legs and body straight and "wind milling" her arms backward about her shoulders, and then her entire body will tilt backwards.

TWISTS
1. TORQUE TWIST-Even non-athletic people can generally stand on a hard surface and twist their 180 degrees or more by pushing off the floor with their feet. Similarly, gymnasts can initiate twists by "pushing" with their feet against the floor. As with somersaults, the forces that initiate the rotation can be controlled easily if the gymnast "throws" her arms in the direction of the twist before her feet loose contact with the floor.
2.TORQUE FREE TWIST WITH ANGULAR MOMENTUM- No torque whatsoever is applied to initiate this twisting. Suppose a gymnast has initiated a stable somersault and is in the"layout" position. She is no longer touching the floor and her body possesses a lot of angular momentum through her left to right axis. Now the gymnast "throws" her right arm above her head and her left arm down to her side, moving her arms in a clockwise rotation. Her lower body then reacts by rotating counterclockwise.
3.TORQUE FREE TWIST WITH ZERO ANGULAR MOMENTUM- This is called the "cat twist." Gymnast are able to rotate their bodies about the head-to-toe axis even though the body has no angular momentum and no external torques are applied. Like a cat being held upside down who is able to perform a series of motions before landing with four feet on the ground, a gymnast can,with the right technique do this too.