通过质点的运动方程说明速度和加速度的数值计算方法。通过图片说明：当时间间隔足够小的时候，速度和加速度的瞬时值可用平均值代替。-By the equation of motion of the particle velocity and acceleration of the numerical method. Photo caption: when the time interval is small enough, the available average instead of the instantaneous value of the velocity and acceleration.