1. The problem statement, all variables and given/known data There are three boxes stacked on top of each other. Each of the boxes has a mass of 250 kg. There is a chord attached to the bottom box applying a force of 7,000N. The coefficient of static and kinetic friction are: μs = .950 and μk = .900. What is the work net if the boxes are pulled 5 meters? What is the change (change) in velocity of the boxes if they're moved 5 meters? 2. Relevant equations Work = mass*acceleration*distance Work = F*d friction = μ * Normal Force 3. The attempt at a solution Total mass of the boxes is 750kg. I'm guessing I have to find the Work done by friction and subtract it from the work done by the force. The amount of work done to the box is 7,000N*5m which is 35,000 J. The work done by kinetic friction is μk*Normal Force = .900*(750kg*cos(0°)) = 675 N * 5m = 3,375 J of work against the boxes as they slide 5 meters. The work done by static friction is μs*Normal Force = .950*(750kg*cos(0°)) = 712.5 N = 712.5N* <--------------So far is this right? What do I do next from here if this is right since static friction doesn't cover any distance?