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NARA [144]
3 years ago
9

A cable that weighs 8 lb/ft is used to lift 900 lb of coal up a mine shaft 650 ft deep. Find the work done. Show how to approxim

ate the required work by a Riemann sum. (Let x be the distance in feet below the top of the shaft. Enter xi* as xi.)
Physics
1 answer:
tia_tia [17]3 years ago
6 0

Answer:

Total Work=2275000 ft-lb

Explanation:

According to Riemann sum approximate for work needed to lift the cable:

W= \lim_{n \to \infty} \sum_{i=1}^n8x_i\Delta x

Sine we have to add 650 terms because distance 650 ft, we will us the integration.

W=\int\limits^a_b {f(x)} \, dx \\W=\int\limits^{650}_0 {8x} \, dx \\W=[4x^2]_0^{650}\\W=4(650)^2-0^2\\W=4*422500 ft-lb\\W=1690000 ft-lb

Work done on lifting:

W_1=900*650\\W_1=585000 ft-lb

Total Work= W+W_1

Total Work=1690000+585000

Total Work=2275000 ft-lb

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