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General Discussion => Other Discussions => Math and Science => Topic started by: Yeong on September 12, 2012, 03:17:02 pm

Title: Calc II Work Question Help D:
Post by: Yeong on September 12, 2012, 03:17:02 pm

All right, I have this question:
A tank is is half full of oil that has a density of 900kg/m3. Find the work W required to pump the oil out of the spout. (Use 9.8 for g and 3.14 for pi. Round your answer to three significant digits.)

(http://img.removedfromgame.com/imgs/6-4-022alt.gif)

r=3
h=1

I don't know how to work this one since the tank is only half full. :\ Apparently diving the full one by 2 doesn't work. Why is that?

EDIT: So for full one, I know that I do integral (900*9.8*pi(9-y^2)*(4-y)) from -3 to 3.
So if I want to do the half one, (900*9.8*pi(9-y^2)*(7-y)) from 0 to 3, right?

Title: Re: Calc II Work Question Help D:
Post by: ruler501 on September 12, 2012, 05:38:02 pm

Are you given the equation for the tank or can you assume its a sphere with a spout on top?
If you can assume its a sphere I'd use the equation for that otherwise integrate the function solved for x for -3 to 0 I'd assume(assuming that the bottom is -3 and top is 3)