In Figure P$4\mathrm{.}25,$ m$1=9\mathrm{.}5$ kg and m$2=3\mathrm{.}5$ kg$.$ The coefficient of static friction between m$1$ and the horizontal surface is $0\mathrm{.}50$ while the coefficient of kinetic friction is $0\mathrm{.}30.$

Figure P$4\mathrm{.}25$

$($a$)$ If the system is released from rest, what will its acceleration be$?$

m$/$s$2$

$($b$)$ If the system is set in motion with m$2$ moving downward, what will be the acceleration of the system?

m$/$s$2$Figure P$4\mathrm{.}25$