Physics problem?

Question

Bricklaying. 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.

If the brick has mass 1.80 kg and is to reach a maximum height of 3.6 m above its initial position on the compressed spring, what distance must the bricklayer compress the spring initially? (The brick loses contact with the spring when the spring returns to its uncompressed length.)

I need some help with this problem. I have no idea what to do. Please show me the steps on getting the answer. Thanks a ton!

Answer 1

This is best solved using conservation of energy

The spring will store energy as
.5*k*x^2
where x is the compressed distance

When the spring is released it will get converted to kinetic energy of the flying brick, which will convert to PE as the brick gains altitude. Since the question states from the compressed position, the equation is
.5*450*x^2=1.80*9.81*3.6
x=0.532 m

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