Three boxes rest side-by-side on a smooth horizontal floor. Their masses are 1.05 kg, 3.55 kg, and 5.20 kg, with the 3.55 kg one in the center. A horizontal force of 33.0 N pushes on the 1.05 kg mass which pushes against the other two masses. What is the contact force between the 3.55 kg and 5.20 kg boxes? Three boxes rest side-by-side on a smooth horizontal floor. Their masses are 1.05 kg, 3.55 kg, and 5.20 kg, with the 3.55 kg one in the center. A horizontal force of 33.0 N pushes on the 1.05 kg mass which pushes against the other two masses. What is the contact force between the 3.55 kg and 5.20 kg boxes? @Physics

Question

Three boxes rest side-by-side on a smooth horizontal floor. Their masses are 1.05 kg, 3.55 kg, and 5.20 kg, with the 3.55 kg one in the center. A horizontal force of 33.0 N pushes on the 1.05 kg mass which pushes against the other two masses. What is the contact force between the 3.55 kg and 5.20 kg boxes?  Three boxes rest side-by-side on a smooth horizontal floor. Their masses are 1.05 kg, 3.55 kg, and 5.20 kg, with the 3.55 kg one in the center. A horizontal force of 33.0 N pushes on the 1.05 kg mass which pushes against the other two masses. What is the contact force between the 3.55 kg and 5.20 kg boxes?  @Physics

anonymous · Answer

Use the applied force and the total mass to compute the acceleration, which must be the same for all three masses, since they are in contact.  Then use the acceleration and the mass to compute the contact force on the last box.