也吸引了不少研究兴趣. 本文提出了一个力算符的定义，利用它可以非常方便地重新得到之前的结果. 当阱壁随时间移动时，

该算符的正确性也得到了数值验证. 这个方法的优点在于避免先引入有限深方势阱计算平均力后再取阱深为无限大的极限

过程. 计算表明，在量子情形下引入含时正则变换再定义力算符的方法既不正确也无必要.

is an exercise that is frequently met in quantum mechanics textbooks. Recently，it also attracts interesting in the

study of quantum nonequilibrium processes. In this paper，a force operator is proposed and is utilized to re-obtain

previous result. Its correctness is as well proved in the case of one wall moving at constant velocity. The advantage

of the operator is that a process of taking limit does not need，where one has to calculate the mean force for a finite

square-well potential first and to take the potential-depth be infinite later. The computations show that，in quantum

regime using a time-dependent canonical transformation to define a force operator is neither correct nor essential.