# Calculate the work to pump water out of tank

• Feb 17th 2010, 03:48 PM
bfpri
Calculate the work to pump water out of tank
An aquarium 2 m long, 1 m wide, and 1 m deep is full of water. Find the work needed
to pump half the water out of the aquarium. (The density of water, p, is 1000 kg/m3,
and acceleration due to gravity, g, is 9.8 m/s2.)

So in order to truly understand how to do these kind of problems I decided to find different ways to solve this problem. Since you can integrate with respect to dx or dy, for dx i was wondering if you could integrate with respect to the 2m side like so

*edit..ugh its not letting me post the pictures so i'll just give the link...http://img19.imageshack.us/img19/2024/boxid.gif

$\displaystyle \int(1+y)(1)pgdx$ from x=0 to x=1. But when i do, i get the wrong answer, 4900 J. The answer should be 2450 J =/
• Feb 18th 2010, 06:47 AM
bfpri
bump
• Feb 18th 2010, 09:40 AM
Calculus26
you're pumpimg upward not sideways.

so you're limits are 1/2 to 1

The cross-sectional area is 2

and the dist ance pumped is 1- y

the Integrand is then 2(1-y) integrated from 1/2 to 1