physics
posted by zeke .
A 1200kg car rolling on a horizontal surface has a speed v= 65km/h when it strikes a horizontal coiled spring and is brought to rest in a distance of 2.2 m. What is the spring stiffness constant of the spring?

KEcar=PEspring
1/2 m v^2= 1/2 k x^2
solve for k. 
8.1*10^4

PE=1/2kx
8.1x10^4