1. The problem statement, all variables and given/known data A body of mass m = 2.5kg is on a frictionless inclined plane (by 40°). At an height of h = 1.6m. On the bottom of the plane there's a spring, which at rest has an extension of 30cm. If the spring is compressed maximum of 12cm, what's the "k" of the spring? 2. Relevant equations 3. The attempt at a solution Alright, there is conservation of energy because there is no friction. mgh = 1/2kx^2 But there is an inclined plane so ... mg(h/sen40) = 1/2kx^2 Now, the only step I don't fully get, what is X? I thought x would be: 30cm - 12cm = 18cm. So I could solve for k. Is this right? Thanks.