A copper roof is being installed on a 300 ft tall building. A copper tile is dropped, and falls to the ground. Assume that there is no air resistance, and that the temperature of the copper tile stays constant (at 80oF) during its fall to the ground. When the copper tile hits the ground, all of its kinetic energy is converted into thermal energy, with no heat lost in the process. What is the temperature of the copper tile after it comes to rest on the ground?
Given: Cu; T1 = 80oF; z1 = 300 ft; z2 = 0 m
Assume: Q = W = ?KE = 0 (the initial and final velocities are both 0 – the energy change in the fall is potential energy); The copper is an incompressible substance with constant specific heats: c = 0.092 Btu/lbm-R
What will be an ideal response?
Solution: (a) The First Law for this closed system reduces to
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