A bucket that weighs 4 lb and a rope of negligible weight are used to draw water from a well that is 90 ft deep. The bucket is filled with 40 lb of water and is pulled up at a rate of 1.5 ft/s, but water leaks out of a hole in the bucket at a rate of 0.15 lb/s. Find the work done in pulling the bucket to the top of the well.

Question

Yusuf Klein

Mathematics

13 February, 17:17

A bucket that weighs 4 lb and a rope of negligible weight are used to draw water from a well that is 90 ft deep. The bucket is filled with 40 lb of water and is pulled up at a rate of 1.5 ft/s, but water leaks out of a hole in the bucket at a rate of 0.15 lb/s. Find the work done in pulling the bucket to the top of the well.

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Keely Palmer · Answer 1

The work on the bucket is a function of height--->h

dwork = F (h) * dh

dwork = weight (h) * dh

weight (t) = 44 - 0.2t

but t = h/v

weight (h) = 44 - 0.2 (h/v) - - - >[44 - 8] = 36 lbs at top

work = ∫ weight (h) * dh

work = ∫[44 - 0.2 (h/v) ] dh ft

work = ∫[44 - 0.1h] dh ft

work = 44h - 0.1*0.5*h^2 ft

work = 44*80 - (0.1*0.5*80^2) = 3200 ft-lbs