# Yurchenko Double Pike by Simone Biles Incredible physics

Gymnastics is a Extremely difficult sports are not just extreme sports for Olympic athletes like five-time (so far) medalist Simone Byers. Physics is also very challenging. Let’s consider some seemingly simple things, such as flipping.

In all four women’s gymnastics, there will be some form of flipping: the floor, the barbell, the vault, and the beam. This is one of the two types of spins that gymnasts can perform in the air. In physics, flipping is a rotation from head to toe about an imaginary axis passing through the gymnastâ€™s hips. For the second type of rotation, twisting, imagine an axis from their head to toe.

Maybe it’s easier to just see them. These two animations were created in Python. (You can see the code here and here.)

Gymnasts can actually perform both types of rotation at the same time-that’s why the sport looks so interesting. In physics, we call this kind of motion “rigid body rotation”. However, it is clear that humans are not rigid, so the mathematics to describe this rotation can be very complicated. For the sake of brevity, let us limit the discussion to flips only.

There are three kinds of flips. There is a layout in which the gymnast keeps the body in a straight position. There is a barracuda whose hips are bent at an angle of about 90 degrees. Finally, there is a fold, and the knees are pulled up toward the chest.

As far as physics is concerned, what is the difference?

Rotation and moment of inertia

If you want to understand the physics of rotation, you need to consider the moment of inertia. I know this is a strange-sounding term. Let’s start with an example involving ships. (Yes, boat.)

Suppose you are standing on the pier, next to a small boat floating there, not tied up. What happens if you put your feet on the boat and push it? Yes, the ship left-but it did something else.Boat also accelerate Move away with it. This speed change is acceleration.