Calculating Work for Pumping Liquid in a Vertical Cylindrical Tank

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SUMMARY

The discussion focuses on calculating the work required to pump liquid from a vertical right circular cylindrical tank measuring 32 feet high and 8 feet in diameter, filled with liquid weighing 62.4 lb/ft³. The incorrect initial calculation yielded 31,948.8 ft-lb, while the correct answer is 1,605,922 ft-lb. Key errors included not accounting for the varying heights of liquid layers and neglecting the area of the cylinder in the calculations. Proper integration techniques and understanding of the physical setup are crucial for accurate results.

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Homework Statement


A vertical right circular cylindrical tank measures 32 feet high and 8 feet in diameter. It is full of liquid weighing 62.4 lb / ft^3 How much work does it take to pump the liquid to the level of the top of the tank?


Homework Equations


h=32
d=8 (radius = 4)
liquid weight = 62.4 lb / ft^3


The Attempt at a Solution


1. integral (0 to 32) (62.4x) dx
2. (156/5)x^2 | (0 to 32)
3. answer: 31,948.8

actual correct answer: 1,605,922 ft-lb
 
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whatlifeforme said:

Homework Statement


A vertical right circular cylindrical tank measures 32 feet high and 8 feet in diameter. It is full of liquid weighing 62.4 lb / ft^3 How much work does it take to pump the liquid to the level of the top of the tank?


Homework Equations


h=32
d=8 (radius = 4)
liquid weight = 62.4 lb / ft^3


The Attempt at a Solution


1. integral (0 to 32) (62.4x) dx
This (above) is way off.

Have you drawn a sketch of a typical "layer" of water? Each of the layers has the same volume, and hence the same weight, but a layer at the bottom of the tank has to be lifted all the way to the top, while the layer at the top doesn't have to be lifted at all.

I don't see any accounting for this in your work.
whatlifeforme said:
2. (156/5)x^2 | (0 to 32)
3. answer: 31,948.8

actual correct answer: 1,605,922 ft-lb
 
hi whatlifeforme! :smile:

ok-ish, but you haven't used the area of the cylinder! :wink:
 

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