Thank you for your reply. The m2 can move upwards and downwards, in two direction. The second question is what I concerned. I don't know how to write the equation to represent this.
Here I want to analyse the force imposed on m1 and m2 while using the second Newton law.
The top view of the system shows like below, thus gravity force is not considered, m2 can only move along the vertical line, and one torsion spring link m1 and m2. The length between m1 and spring is L...