1. The problem statement, all variables and given/known data A cap on a steel pin has a mass of m=500g and the pin has an angle of 50 degrees from the horizontal plane. The kinetic friction coefficient between the steel pin and the cap that glides down is uk=0,1. There is a spring at the bottom of the steel pin with spring konstant k=300 N/m. The distance travelled by the cap before it reaches the spring is d=1.16m. a) What speed does the cap have as it reaches the spring? b) What maximum change in length will the spring experience? (This is where I need help) [PLAIN]http://beborche.net/blandat/hylsan.jpg [Broken] 2. Relevant equations From a) I know that the speed is v=4 m/s, and that the acceleration of the cap along the pin is 6.9 m/s². (g*sin(50) - uk*N = 7.51 - 0.31 = 6.9) 3. The attempt at a solution Shouldn't one be able to put up the equation like this: ma = -kx and then solve for x? 0.5*6.9 = -300x <=> x = - 0.5*6.9 / 300 = 0.0115meters = 1.15 cm The answers have a very different answer. I can state it here if you'd like, but does anyone know where I go wrong? Thanks. Edit: I have to use Mechanics laws and Force laws for this task.