A portable free fall experimental device that does not require a darkroom and can collect data in real-time. The teacher completed the assignment in 5 minutes, and the students measured the local gravity acceleration g within 5 minutes, with an error of ≤ 1%. And seal the falling channel, so that the ball does not land. Can be used for experiments: classical free fall, measuring g (single or double door); Uniform acceleration linear motion: verification of v=gt, s=189gt ²; Research on Air Resistance: Comparison between Steel Balls and Aluminum Balls; Expansion: Synchronize with mobile phone accelerometers and compare theoretical values with measured values.