Physics
posted by Lowell .
A 1200 kg car rolling on a horizontal surface has spped v= 65 km/h when it strikes a horizontal coiled spring and is brought to rest in a distance of 2.9 m. What is the spring stiffness constant of the spring?

This problem can be solved with the conservation of energy. The total amount of energy in the car is the same before and after the collision with the spring. The car's kinetic energy before the collision is completely converted to spring potential energy after the collision.
1/2 * m * v^2 = 1/2 * k * x^2
Plug and chug, solve for k 
99173.55 kg s^2