Hi. I have a physics question. I cannot get the right naswer. The question: Three boxes rest side-by-side on a smooth horizontal floor. Their masses are 1.10 kg, 3.45 kg, and 5.55 kg, with the 3.45 kg one in the center. A horizontal force of 20.0 N pushes on the 1.10 kg mass which pushes against the other two masses. What is thte contact force between the 3.45 kg and 5.55 kg boxes? My solution: I know that the force applied (20.0 N) is not constant throughout. However, acceleration of the full system is. Therefore I thought I could use Newton's 2nd Law. Fnet = ma. Fnet of mass 1.10 kg = ma rearranging gives a = 18.18 m/s^2. Fnet of mass 3.45 = ma = 62.7 N I thought this would be my contact force as this is the force that the 3.45 kg block pushes against the 5.55 kg box?/ Isn't this the answer? Can someone point me in the right direction or help me out.?? Thanks.