In the figure below a 1.24 kg block is held at rest against a spring with a force constant k = 700 N/m. Initially, the spring is compressed a distance d. When the block is released it slides across a surface that is frictionless, except for a section of width x = 4.85 cm that has a coefficient of kinetic friction μk = 0.357. Calculate d such that the block's speed after crossing the rough patch is 2.23 m/s. Sorry I can't post the picture. This was how I was figuring out the problem, but that isn't working. k ( L_1 + x)^2 - coefficient sign (u_k)mgx = 1/2mv_f^2 + mg(0) since d= L_1 + x and F= kd substitute values to get L_1 and then find d That is how i was doing it but I can't figure it out. Is there a more simple explanation or way to figure out this problem? Thanks.