1. The problem statement, all variables and given/known data I was tasked with finding the equations of motion for an the airplane model pictured below. Mass 1 and Mass 3 represent the wings. K1 and K2 are linear springs that represent the stiffness of the wings. M2 is the fuselage and M4 is the landing gear. K3 is the linear spring that represents the stiffness of the landing gear structures. The circle marked landing gear is not the landing gear. It is actually the ground. And the linear spring between them, K4, is a representation of the stiffness of the tires. This was a mistake. My apologies. 2. Relevant equations N/A 3. The attempt at a solution Here is my solution: My professor marked them wrong, but did not say why. Can one of you enlighten me please? This is all. Thank you.