1. The problem statement, all variables and given/known data A box of unknown mass slides across a frictionless floor with an initial speed of 4.7 m/s. It encounters a rough region where the coefficient of friction is µk = 0.3 Part 1: What is the shortest length of rough floor which will stop the box? Part 2: What is the shortest length of rough floor which will stop the box? 2. Relevant equations vf^2 = vi^2 + 2a delta x. Frictional force = mew times the normal force 3. The attempt at a solution Final velocity = 0, so 0 = 4.7 ^2 + 2A delta x. A = the frictional force. How can I determine the normal force (and after that, the frictional force, and after that, the change in distance) if I don't know the weight of the box? Is there another way to do this problem?