Let me just reproduce the question here
A jack-in-the-box is made using a spring of natural length 0.2m and modulus 100N and a 'jack' of mass 0.5 kg. When the lid is closed the spring is compressed to a length of 0.1m. Assuming that the spring is vertical throughout, calculate the maximum distance that the 'jack' will rise when the lid is suddenly raised.
The answer is 0.180m but I can't seem to get that answer!!!!!