The net force is force applied + force friction ( which is negative ) Unfortunately for some reason the numbers are negative, could you ask your teach about that?
Btw, left is usually force fric. which makes it negative
Using conservation of energy and momentum we get m1*v1=(m1+m2)*v2 so rearranging for v2 and plugging the given values in we get: (200000kg*1.00m/s)/(21000kg)=.952m/s