1. The problem statement, all variables and given/known data A 8000 kg freight car rolls along rails with negligible friction. The car is brought to rest by a combination of two coiled springs as illustrated in the figure below. Both springs are described by Hooke's law with k1 = 1600 N/m and k2 = 3000 N/m. After the first spring compresses a distance of 15.0 cm, the second spring acts with the first to increase the force as additional compression occurs as shown in the graph. The car comes to rest 50.0 cm after first contacting the two-spring system. Find the car's initial speed. 2. Relevant equations U=1/2kx^2 KE=1/2mv^2 3. The attempt at a solution i tried to set U and KE equal and solve for v but its not really working out. i tried the equation 1/2(k1)(x1)^2+1/2(k2)(x2)^2=1/2mv^2. the problem is confusing because k2 and x2 are not explicitly expressed.