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Exploring Energy ConceptsA 2.5 × 3.5 × 6 in. brick whose
Chapter 2, Problem 4P(choose chapter or problem)
A \(2.5 \times 3.5 \times 6\) in. brick whose density is \(120 \mathrm{lb} / \mathrm{ft}^3\) slips off the top of a building under construction and falls \(69 \mathrm{ft}\). For \(g=32.0 \mathrm{ft} / \mathrm{s}^2\), determine the change in gravitational potential energy of the brick, in \(\mathrm{ft} \cdot \mathrm{lbf}\).
Questions & Answers
QUESTION:
A \(2.5 \times 3.5 \times 6\) in. brick whose density is \(120 \mathrm{lb} / \mathrm{ft}^3\) slips off the top of a building under construction and falls \(69 \mathrm{ft}\). For \(g=32.0 \mathrm{ft} / \mathrm{s}^2\), determine the change in gravitational potential energy of the brick, in \(\mathrm{ft} \cdot \mathrm{lbf}\).
ANSWER:Step 1 of 4:
The density and volume of a brick are given. The brick falls from the top of the newly constructing building. We are going to find the change in gravitational potential energy of the brick. We need to convert the units into SI standard to solve the problem easily.
Volume of the brick V = 2.5 × 3.5 × 6 in3 = 52.5 in3 = 0.00086 m3
The density of the brick ρ = 120 lb/ft3 = 1922.22 kg/m3
Height of the building h = 69.0 ft = 21 m
The acceleration due to gravity g = 32.0 ft/s2 = 9.81 m/s2