The coefficient of static friction is 0.60 between the two blocks in figure. The coefficient of kinetic friction between the lower block and the floor is 0.20. Force causes both blocks to cross a distance of 5.0 m, starting from rest. What is the least amount of time in which this motion can be completed without the top block sliding on the lower block? this is wht i think as long at the two blocks are moving together they have the same accleration. bottom box: x: Ff= ukFn= 0.20*7kg*9.81m/s/s=7*a top box: x: Ft-ff= Ft- usFn= 0.60*4*9.81m/s/s=4*a and then cant you just use the kinematics equation xf=xi+vt+.5at^2 to find the time?