动力学中有五个重要规律,即牛顿定律、动量定理、动能定理、动量守恒定律、能量守恒定律,如果把这些规律比作一棵樱桃树的话,牛顿第二定律就是这棵树的树干,利用牛顿第二定律可以定量解决恒力作用下的匀变速运动问题.在变力作用下做变加速运动(非匀变速运动)时,首先,可考虑用微元法解题.微元法的具体做法是:在时间△t很短或位移△s很小时,非匀变速运动可以看作匀变速运动,对牛顿 There are five important laws of dynamics, that is, Newton’s law, momentum theorem, kinetic energy theorem, law of conservation of momentum, law of conservation of energy, if these laws are compared to a cherry tree, Newton’s second law is the tree trunk, The Newton’s second law can be used to quantitatively solve the problem of uniform speed motion under constant force.When variable speed motion (non-uniform speed motion) is made under variable force, The specific approach is: time △ t is very short or displacement △ s is small, non-uniform speed motion can be seen as uniform speed motion, Newton