建立直角坐标系是应用牛顿第二定律解题过程中一个常用的方法.建立直角坐标系通常是选用共点力的作用点为坐标原点,坐标轴的方向选择则应根据实际情况来确定.通常有3种建立方式,即按照分解力的思路建立坐标系,或按分解加速度的思路建立坐 The establishment of Cartesian coordinate system is a common method used to solve the problem of Newton’s second law.The establishment of Cartesian coordinate system usually selects the point of common force as the origin of coordinates and the choice of the direction of coordinate axis should be based on the actual situation.Usually There are three ways to build, that is, in accordance with the idea of ​​decomposition of the establishment of coordinate system, or decomposition of the idea of ​​acceleration set up