1 Physics -- Rotational Dynamics

An Olympic high diver starts his dive with a double somersault while keeping his arms neatly tucked to his chest. But as he approaches the pool surfaces, his arms stretch over his head to a point and his entire body becomes streamlined during the impact with the water. What is the reaso...

An Olympic high diver starts his dive with a double somersault while keeping his arms neatly tucked to his chest. But as he approaches the pool surfaces, his arms stretch over his head to a point and his entire body becomes streamlined during the impact with the water. What is the reason for his routine?

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I, personally loved this problem. Though I am not that much interested in playing sports on my own, I love the beauty of physics behind each sport, and the way physics beautifies each sport.

Before approaching the question, let's know how diving is scored in Olympic games. The judges score looking at the starting position, approach, height, flight, and entry. The higher jump with a maximum number of somersaults and a perfect entry with a minimal splash is always considered the best one.

In the Olympic games, before taking off from the springboard, the diver must make sure to have shifted ownself a little further to prevent hitting the board during the dive. Then, the diver tucks arms and legs close to the chest to make sure he/she has gained a nearly spherical shape. This decreases the moment of inertia allowing the diver to have maximum possible somersaults, in order to score as high as possible. The most crucial part of diving competitions in Olympics is the entry. The lesser the splash, the greater will be the score. Although there are no written rules for this part, judges score the dive, looking at the beauty of the jump reflected by the splash.

While reaching the surface of the water, the divers stretch their own hands over the head and attend a streamlined body in order to enter with minimal splash. They have their hands out, thumbs interlocked, and grabbed on the top by fingers. This pokes a air-filled hole in the water, and the entire body of the diver is supposed to enter the pool through this hole. This decreased the area of impact, thereby decreasing the splash generated by the impact. In addition, this prevents the formation of an air cavity around the body of the diver thereby preventing the formation of an after splash. This creates what is called a rip entry, named after the similar sound of ripping a page.

A perfect combination of this routine guided by the laws of physics is what makes a perfect dive. Prefer watching the dive performed by Matthew Mitcham (from team Australia) at Beijing 2008, as it is the highest-scoring diver performed to date.

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