牛顿第一定律指出:一切物体在不受任何外力作用时,总保持静止或匀速直线运动状态。它揭示了一切物体都具有惯性,同时也指出了力是改变物体运动状态的原因。在实际生活中,找不到不受任何外力的物体,物体总是受了多个力,其运动状态可能改变,也可能不变。当物体运动状态不发生改变时,我们称此时物体处于平衡状态;反之则物体处于非平衡状态。我们要会对物体进 Newton’s first law states that: All objects remain stationary or move at a constant linear velocity without any external force. It reveals that all objects have inertia, and also points out that force is the reason for changing the state of motion of an object. In real life, the object can not be found without any external force, the object is always subject to multiple forces, the state of their movement may or may not change. When the state of motion of the object does not change, we call the object in balance at this time; otherwise, the object is in an unbalanced state. We want to get into the object