人教版普通高中课程标准实验教科书《物理》必修2的《教师教学用书》,在第15页上对验证机械能守恒定律作了如下的误差分析:“重物和纸带下落过程中要克服阻力,主要是纸带与计时器之间的摩擦力,计时器平面不在竖直方向,纸带平面与计时器平面不平行是阻力增大的原因.电磁打点计时 PEP Ordinary High School Curriculum Standards The experimental textbook “Physics” compulsory 2 “Teacher’s Teaching Book”, on page 15 of the verification of mechanical energy conservation law made the following error analysis: "The weight and tape falling process to overcome resistance , mainly the friction between the tape and the timer, the timer plane is not in the vertical direction, the tape plane is not parallel to the timer plane is the reason for the increase in resistance. Electromagnetic timing