A giant toy car with big wheels has a total mass (including the wheels) of 0.24 kg. The car has 4 wheels and each wheel has radius of 3.4 m and a moment of inertia of 0.25 kg m2. The car is attached to a horizontal spring. The spring is inititally unstretched and the car is given an initial speed of 3.4 m/s away from the spring. The car moves forward 0.34 m before it stops and is pulled back by the spring. The wheels roll without slipping the entire time.
What is the spring constant?