Engineering Board Exam Reviewer · Applications: Centroid, Work, and Moment of Inertia · medium
A 40-m cable weighing 2.5 kg per meter hangs from the top of a building with a 50-kg load at its lower end. How much work, in kilojoules, is done in pulling the entire cable and load up to the top? Use g=9.81 m/s2.
- 19.62
- 58.86
- 78.48
- 39.24
Answer
D. 39.24
Solution
Load: 50(9.81)(40)=19,620 J. Cable: a piece at depth y is lifted y meters, so 0402.5(9.81),y,dy=24.525·800=19,620 J. Total =39,240 J =39.24 kJ.
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