Winthrop

2 equations: Work spring = work of gravity: 0.5kx^2 = mgh Force spring = Force of gravity + Force of car: kx = mg + m(4g) Use the force equation to find that kx = 5mg, then substitute that into the work equation to get 0.5(5mg)x = mgh. Do some math and ge...

EDIT: h = 11.8 + x, x being the displacement of the spring once the car lands on it. Otherwise you'll get 2.5 instead of 1.5 when solving for x.