1. The problem statement, all variables and given/known data An accident safety system uses a spring to absorb the energy of a car before the car collides with a bridge abutment. The vehicle has a mass of 1000kg and the design calls for stopping a car moving at 5m/sec (11.2 mi/hr) in 0.5m. Find the spring constant k 2. Relevant equations F=kx -> k=F/x 3. The attempt at a solution I am having trouble finding the force of the collision. It is needed to find k, is it not? I was thinking I may need to use a kinematics equation to do this and solve for the acceleration (deceleration in this case).