Compute all parts of given problem:
Problem: An ingenious bricklayer builds a device for shooting bricks up to the top of the wall where he is working. He places a brick on a vertical compressed spring with force constant k = 450 N/m and negligible mass. When the spring is released, the brick is propelled upward.
Part I: If the brick has mass 1.80 kg and is to reach a maximum heights of 3.6 m above its initial position on the compressed spring, what distance must the bricklayer compress the spring initially? Express your answer using two significant figures.
Part II: The brick loses contact with the spring when the spring returns to its uncompressed length. Why?
I don't understand how to get the answer. Can you please help me with this problem?