Hi, I have been given this problem to do as extra credit: An inventive child named Pat wants to reach an apple in a tree without climbing the tree. Sitting in a chair connected to a rope that passes over a frictionless pulley, Pat pulls on the loose end of the rope with such a force that the spring scale reads 250 N. Pat’s true weight is 320 N, and the chair weights 160 N. Show that the acceleration of the system of Pat and the chair is upward and find its magnitude. Find the force Pat exerts on the chair. Diagram: http://www.geocities.com/newc00l/physics.html I made 3 free body diagrams, one of the child with the chair, one of the spring scale and one of the spring inside the spring scale, but am at a loss to generate the necessary equations and am stuck. Thanks in advance for any help.