Abox slides across a frictionless floor with an initial speed v = 3.6 m/s. it encounters a rough region where the coefficient of friction is µk = 0.7. a) what is the shortest length of rough floor which will stop the box? x = 0.9436 m * 0.9436 ok : apply the work-energy theorem. : according to the work-energy theorem, the net change in kinetic energy of the box is equal to the work done on the box by the external forces. what are those forces? which ones do work? relate the work to the distance over which the forces act. b) if instead the strip is only 0.56 m long, with what speed does the box leave the strip?