1. The problem statement, all variables and given/known data In figure (a), four identical crates weighing 2,000 lb each are stacked one on top of another, and in figure (b) a simple model for determining the deformation of the stack of crates is shown. In this model, each spring has the same stiffness k = 4,500 lb/in. and the forces are determined using the following idealization. Half the weight of the top crate is applied to point A and half to point B. Similarly, the half the weight of the next crate is applied to point B and half to point C, and so on. Determine the deflections δA, δB. http://imgur.com/XhWr2YE Hint given: Begin by drawing FBDs of joints A, B, C and D. Starting from the top, you should find that each spring carries progressively larger weight. Note that the problem statement requests deflections, which are not necessarily the same as stretches. For the bottom spring, anchored at one end, its deflection is identical to its stretch. For all the spring above it, however, the deflection is the cumulative sum of the stretches below and including that spring. 2. Relevant equations Spring Law: Fs=kδ=k(L-L0) 3. The attempt at a solution A 1000lb = 4500 (lb/in) (δ+B+C+D) B 2000lb = 4500 (lb/in) (δ+C+D) C 2000lb = 45000 (lb/in) (δ+D) D 2000lb = 4500 (lb/in) δ I don't know where I'm going wrong here. No actually distances are given so I'm assuming you just have to solve for δ, but is my approach correct? Thank you for any help!