An athlete diving off a high springboard can perform a variety of exercises in the air before entering the water below. Which one of the following parameters will remain constant during the fall ?

When an athlete dives off a springboard, the only external force acting on them is gravity. Gravity acts through the athlete's center of mass, meaning the net external torque about the center of mass is zero. According to the principle of conservation of angular momentum, if the net external torque is zero, the angular momentum remains constant throughout the motion. While the athlete can change their moment of inertia by tucking or extending their limbs to alter their rotation speed, the product of the moment of inertia and angular velocity (angular momentum) stays the same. Linear momentum changes because gravity accelerates the body downward. Kinetic energy increases as gravitational potential energy is converted during the fall. The moment of inertia varies as the athlete changes their body configuration to perform exercises. Thus, only angular momentum is conserved during the flight.

Sources

1. [1] Environment and Ecology, Majid Hussain (Access publishing 3rd ed.) > Chapter 8: Natural Hazards and Disaster Management > Types of Landslides > p. 41