Football flies in the air, and then there will be eddy current, and the force of eddy current on football is unstable, which causes football to flutter up and down.

Attachment: Causes of Volleyball Drift:

1. Non-rotating objects fly in the air, because there is no rotating shaft, their flight trajectory is unstable and easy to swing. 2. When hitting the ball, due to the concave deformation of the hit part of the ball, the gas pressure in the ball increases, making other parts of the ball convex deformation. When these parts of the sphere return to their original shape, the interior of the sphere impacts the depressed and deformed parts of the sphere at high speed, but the depressed parts go beyond the original shape and become new protrusions, resulting in reverse deformation, thus repeatedly forming vibration. At the moment of vibration, the sphere has lost its normal shape, thus drifting under the action of aerodynamic force. 3. When the speed of the ball drops to 5 ~ 10 m/s in flight, the ball will be subjected to strong air resistance nearly twice the speed of the ball, and the ball will produce obvious lateral force (vertical wind speed), which always exists during the flight of the ball, but is particularly strong at a specific speed, and then the ball will suddenly stall and naturally form a sinking floating ball under the action of gravity. 4. The material used to make the ball is not completely uniform, and due to the influence of the position and weight of the ball mouth, the substantial center of gravity of the ball is inconsistent with the geometric center of gravity. During the flight of the sphere, the windward area of the center of gravity is small and the wind resistance is small; The windward area of the center of the ball is large, so the ball must rotate around the center of gravity. Because of the swing, the air velocity on both sides of the ball changes, the center of gravity of the ball accelerates and the center of the ball slows down, so the ball floats in the direction of the center of gravity for the first time, and then floats for the second time when the position of the center of gravity/center of the ball changes, so the trajectory of the ball changes constantly. Therefore, when the sphere does not rotate and is in an unstable state, it will tilt, float and fall in the direction of the actual center of gravity.

The shaking of the ball is a random phenomenon and cannot be controlled according to the player's will. But through certain techniques, football players can control the shaking of football to a certain extent.