Stroboscopic photography is a commonly used experimental method to study variable speed motion. In the darkroom, the shutter of the camera is always open, and the stroboscope is sent out every once in

Stroboscopic photography is a commonly used experimental method to study variable speed motion. In the darkroom, the shutter of the camera is always open, and the stroboscope is sent out every once in a while. (1) Method 1: According to △ h = gt 2, g = △ h t 2 is obtained.

Method 2: calculate the instantaneous speed of a certain position (the average speed in a certain period is equal to the instantaneous speed in the middle); Then use v=gt to solve, g = v t.

(2) VB = XAC2T = (28.4-12.5) ×10-22× 0.04m/s =1.99m/s.

Therefore, the speed of the ball passing through point B is 1.99 m/s. 。