Second, observe the approximate angle between the ball and the vertical line every time it bounces, and make corresponding adjustments to make up for the error, so as to ensure that the angle between the ball and the vertical line is as 0 degrees as possible next time.
Third, the concentric drum movement, like its nickname, works together. Only with Qi Xin's concerted efforts can each member keep the ball bouncing to the end and laughing to the end.
Matters needing attention in concentric drum movement:
Each player pulls a rope. After the project started, Qi Xin and Qi Xin worked together to keep the drum surface level and racket the ball. In this process, the players can only grasp the end of the rope and must not touch the drum or other parts of the rope. In addition, at the beginning of the project, the ball fell vertically from 40 cm above the center of the drum surface, so the height of the ball should be greater than 40 cm from the drum surface, that is, the height of the ball should not be less than 40 cm.