牛顿第一定律告诉我们,物体在平衡力的作用下会保持原来的运动状态不变.然而通常情况下,物体的受力并不平衡,运动状态也在变化,那么当物体的运动状态发生改变时,这个改变点就是临界点.临界问题通常伴有“恰好”“最大”“至少”等词语出现.圆周运动由于其极强的瞬时性(如向心加速度的瞬时性以及向心力来 Newton’s first law tells us that the object under the action of the balance will keep the original state of motion unchanged. However, under normal circumstances, the force of the object is not balanced, the state of movement is also changing, then when the object’s movement changes , The change point is the critical point, and the critical problem is usually accompanied by the words “exactly ” “max ” “at least ” etc. Circular motions due to their extremely transient properties (such as the instantaneous acceleration of centripetal And to heart force