In the shown figure, the spring and string is ideal. The spring the stiffness of `100 N//m` and `m = 1 kg` friction exists between mass 2m and surface with coefficient `mu = 0.8`. The system is released with spring from its relaxed position. Based on above data, answer the following question: (take `g = 10 m//s^(2)`)
After what displacement of mass 2m, its velocity becomes maximum ?
A. 4 cm
B. 8 cm
C. 2 cm
D. zero
