Angular momentum + Centrifugal force + water bottle= SUCCESS
I’m sure any kid in school that doesn’t live in a snow cave, has try the water bottle challenge.
Also known “The flip,” as it will henceforth be known, all begins with a flick of the wrist, generating a specific force called angular momentum,
Angular momentum is very similar to the classical sense of momentum, where an object moving will not change its motion unless acted upon by another force. With angular momentum, the same concept is applied to rotation.
As centrifugal force keeps the water at the bottom of the bottle during its spin, that also dictates where the plastic container’s center of gravity is. The heaviest part of the bottle is pulled toward the ground and – TA DA!
Recording the motion and playing it back in slow-motion helps reveal what is going on. As the bottle moves through the air the liquid inside it starts to climb the sides. This increases the bottle’s moment of inertia and so decreases its rotational speed, much like a high diver who extends his arms and legs to slow his spin down.