A 1120 kg car rolling on a horizontal surface has a speed of 60 km/hr when it strikes a horizontal coiled spring and is brought to rest in a distance of 4.5 m. What is the spring constant (in N/m) of the spring? (Ignore nonconservative forces such as friction.)

1/2 k x^2 = 1/2 m v^2

k = m v^2 / 4.5^2

convert 60 km/hr to m/s and calculate