/sci/ - Science & Math

[Anonymous No.4368117]

/sci/ I have a question about a problem.
A hemisphere tank with a radius 6, base is the circle is being filled with water from the bottom. I need to find out how much work is being done.

http://www.calcchat.com/book/Calculus-9e/
(Chap 7, Section 5, Prob 23)

This is easy mostly
pi*r^2 * weight = force
distance = y
My question is why is the distance y?
Why isn't it 6 - y? I know this is an odd question and I'm not sure if anyone can help. I'm just so confused as to why it's y, because how can the distance be a constant in a problem like this?

[Anonymous No.4368121]

>>4368117
I guess y isn't a constant. I worded it wrong.

But whenever I'm EMPTYING a tank, I always would move it like (y-6), because obviously over time I need to empty less and less of the tank. Wouldn't I need to fill less and less of the tank over time? How can I still need to be filling over the same distance?

[Anonymous No.4368130]

>>4368117
Because you need to assume the water under the tank is always RIGHT under the tank. The water always needs to move from 0 to the current disk height, or y