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. Why?)
Solution 46E Step 1: Spring constant of the spring, k = 450 N/m Mass of the brick, m = 1.80 kg Maximum height, h = 3.6 m We can write, the energy during compression = Potential energy at maximum height 2 That is, ½ kx = mgh Where, x - compressed length of the spring g - acceleration due to gravity h - maximum height
