The elastic force makes the coverboard rotate to the second position from the first position so as to expose the opening.
弹力使盖板由第一位置转动至第二位置,使开口得以外露出来。
英语百科
Force
In physics, a force is any interaction that, when unopposed, will change the motion of an object. In other words, a force can cause an object with mass to change its velocity (which includes to begin moving from a state of rest), i.e., to accelerate. Force can also be described by intuitive concepts such as a push or a pull. A force has both magnitude and direction, making it a vector quantity. It is measured in the SI unit of newtons and represented by the symbol F.