retracting spring

• 回动弹簧,释放弹簧,回程用弹簧

retracting spring的用法和样例：

例句

1. If we let go, the elastic energy, as the spring passes through the equilibrium point, is converted to kinetic energy.
   如果我们释放弹簧，那么弹簧经过平衡点时，弹性能就转变为动能。