(a) The distance the bricklayer must compress the spring initially is 0.53 m.
(b) The brick loses contact with the spring when the spring returns to its uncompressed length because the elastic potential energy of the spring has been converted into kinetic energy of flying brick.
When the brick reaches the maximum height, the elastic potential energy of the spring will be converted into potential energy of the brick due to law of conservation of energy.
Ux = P.E
¹/₂kx² = mgh
kx² = 2mgh
x² = 2mgh/k
x = √(2mgh/k)
x = √(2 x 1.8 x 9.8 x 3.6 / 450)
x = 0.53 m
Thus, the distance the bricklayer must compress the spring initially is 0.53 m.
The brick loses contact with the spring when the spring returns to its uncompressed length because the elastic potential energy of the spring has been converted into kinetic energy of flying brick.
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