# Calc 2: Find the work W required to pump the water out ....

• Jan 29th 2010, 07:32 AM
Mathhelpz
Calc 2: Find the work W required to pump the water out ....
• Jan 29th 2010, 09:48 AM
Calculus26
The cross-sections are rectangles all of which are 12 m long and have variable width.

To find the width as a function of y --the height above thr ground use similar triangles.

The distance a cross -section is pumped is 7 -y

The int limits are 0 to 4

See attachment
• Jan 29th 2010, 11:32 AM
ebaines
Don't forget to multiply by g times the densiy of water, which is approximateley 100 Kg/m^3. This gets you the answer in terms of kg-m^2/s^2, or Joules.
• Jan 29th 2010, 12:34 PM
Calculus26
Thanks--- I was thinking density =1kg/L which is true but as you pointed out the units would have been off.

1kg/L tranlsates to 1000kg/m^3 not 100
• Jan 29th 2010, 12:39 PM
ebaines
Quote:

Originally Posted by Calculus26
1kg/L tranlsates to 1000kg/m^3 not 100

Oops! Yes - thanks for catching that!
• Jan 29th 2010, 12:44 PM
Calculus26
The following attachment reflects the changes-- thanks again