In a forward one-and-a-half somersault with three twists, a diver initiates twisting by adjusting their arms and head, causing their somersaulting axis to no longer be parallel to the angular-momentum vector. Near the end of the dive, the athlete realigns their somersaulting axis with the angular-momentum vector, stopping the twisting motion to conserve angular momentum. A forward two-and-a-half somersault with two twists proves that divers can initiate continuous twisting while in midair. In this maneuver, the diver completes over one full somersault before starting to twist, and maintaining the twisting motion doesn't require moving the legs relative to the torso. Somersaults and twists are the fundamental maneuvers in competitive diving, involving rotation around different axes. When a diver combines these maneuvers, their total angular-velocity vector is the vector sum of the somersaulting and twisting angular velocities, with the twist typically being three times faster than the somersault. The moment of inertia, a body's resistance to changes in angular velocity, is greater when its mass is concentrated further from the axis of rotation. A person's somersaulting moment of inertia varies with body position: largest when straight, smaller when piked, and smallest when tucked, allowing for different rotation speeds and control. **Somersault:** is an acrobatic maneuver in which a person rotates their body around an imaginary axis, typically moving head over heels. It can be performed either forwards, backwards, or sideways and is commonly seen in gymnastics, diving, and other athletic activities. The rotation usually occurs with the person's body either in a straight, piked, or tucked position, affecting the speed and control of the movement. **Twist:** A twist is a rotation of the body around an axis running from the head to the toes, typically performed in midair during acrobatic or gymnastic maneuvers. The linear momentum p: $$p = m \cdot v$$ (m is the mass of the body, and v is its velocity) is related to an object's motion in a straight line. The angular momentum L: $$L = I \cdot \omega$$ (I is the moment of inertia, and $\omega$ is the angular velocity) is specifically concerned with its rotational motion. Both quantities are conserved in the absence of external forces or torques, respectively, and they play crucial roles in understanding the dynamics of objects in motion. The moment of inertia I is a measure of an object's resistance to rotational motion around an axis: $$I = \int r^2 dm$$ it depends on the distribution of mass within the object and the distance (r) of each mass element from the axis of rotation. This equation calculates the moment of inertia by integrating over all mass elements (dm) in the body, each multiplied by the square of its distance (r^2) from the axis of rotation. **Video of rotating chair experiment, illustrating moment of inertia.** [](https://upload.wikimedia.org/wikipedia/commons/transcoded/9/93/25._%D0%A0%D0%BE%D1%82%D0%B0%D1%86%D0%B8%D0%BE%D0%BD%D0%B5%D0%BD_%D1%81%D1%82%D0%BE%D0%BB.ogv/25._%D0%A0%D0%BE%D1%82%D0%B0%D1%86%D0%B8%D0%BE%D0%BD%D0%B5%D0%BD_%D1%81%D1%82%D0%BE%D0%BB.ogv.1080p.vp9.webm)  Here is a video of Destin from Smarter Every Day explaining this phenomenon: **Smarter Every Day - Slow Motion Flipping Cat Physics** [](https://www.youtube.com/watch?v=RtWbpyjJqrU)  #### TL;DR "The Physics of Somersaulting and Twisting" showcases the fascinating intersection between human body mechanics and fundamental physical principles. In this paper the author dives deep into how angular momentum and torque are used to generate rotational motion in the body, and how gymnasts can manipulate their bodies to control their movements in the air. The physics involved in somersaulting and twisting primarily revolves around: - **Angular momentum:** It is a measure of an object's rotational motion. In sports like gymnastics and diving, angular momentum is conserved, which means that the total angular momentum before and after a maneuver remains constant, as long as no external forces act upon the athlete. - **Moment of inertia:** It refers to the resistance an object has to changes in its rotational motion. In the context of somersaulting and twisting, an athlete can adjust their moment of inertia by changing their body position. For instance, a tucked position (bent at the waist and knees) results in a lower moment of inertia, allowing for faster rotation, while an extended position (straight body) increases the moment of inertia, slowing down the rotation. - **Torque:** This is the turning or twisting force that causes an object to rotate. In somersaulting and twisting, athletes create torque by pushing off the ground or platform, generating the angular momentum needed for rotation. Understanding the underlying physics enables athletes to optimize their movements and techniques, ultimately enhancing their performance. > ***"The study of somersaulting and twisting physics also highlights the impressive feats the human body can achieve when skillfully harnessing the laws of physics."*** To learn - What is Anglugar Momentum? This seemingly paradoxical scenario is explained by the fact that the cat and the diver can change their body orientation without violating the law of conservation of angular momentum. Adjusting the moment of inertia by changing their body shape, which in turn changes their angular velocity. For example, a diver might bring their arms and legs closer to their body to decrease their moment of inertia, which then causes an increase in their angular velocity, allowing them to rotate in midair. Since the overall angular momentum remains constant, no violation of conservation laws occurs. **Here is a video of a rotating chair experiment illustrating how body shape affects rotation:** [](https://upload.wikimedia.org/wikipedia/commons/transcoded/9/93/25._%D0%A0%D0%BE%D1%82%D0%B0%D1%86%D0%B8%D0%BE%D0%BD%D0%B5%D0%BD_%D1%81%D1%82%D0%BE%D0%BB.ogv/25._%D0%A0%D0%BE%D1%82%D0%B0%D1%86%D0%B8%D0%BE%D0%BD%D0%B5%D0%BD_%D1%81%D1%82%D0%BE%D0%BB.ogv.1080p.vp9.webm)