1. The problem statement, all variables and given/known data A warehouse worker applies a force of 420 N to push two crates across the floor. One crate is 30kg and the other is 40kg. The boxes are touching each other. The friction forces opposing the motion of the crates is a constant 2.0N for each kilogram.. Edit: The question is; Calculate the force exerted by the 40kg crate on the 30 kg crate 2. Relevant equations F=ma 3. The attempt at a solution Just substituted the answers in correctly taking into consideration the friction of 2.0N and got 240N but the answer at the end of the book saids 280N I am not sure where i went wrong. Could someone please help me out.