Monday

October 20, 2014

October 20, 2014

Posted by **Tim** on Saturday, December 17, 2011 at 5:05pm.

- Calculus -
**Damon**, Saturday, December 17, 2011 at 5:18pmr = 2 + 4 (h/10) = 2 + .4 h

surface area = pi r^2

surface area*dh = dV

(volume of slice at surface)

pi r^2 dh = DV

pi (4 + 1.6 h + .16 h^2) dh = dV

thus

pi (4 + 1.6 h + .16 h^2) dh/dt = dV/dt

but we know that dV/dt = 10 in^3/min

so

dh/dt = (10/pi)(1/(4 + 1.6 h + .16 h^2)

when h = 0

dh/dt = 10/(4pi) etc

- Calculus -
**Tim**, Saturday, December 17, 2011 at 5:34pmThanks. I think that I understand the 1st question now. How about the other questions?

- Calculus -
**Damon**, Saturday, December 17, 2011 at 6:05pmYou only need solve for h as a function of time

pi(4 + 1.6 h + .16 h^2)dh/dt = dV/dt =10

(4 + 1.6 h + .16 h^2)dh = (10/pi) dt

4 h + .8h^2 + .0533 h^3 = (10/pi) t

1.26 h + .251 h^2 + .0167 h^3 = t

You have to solve this for h and then r when t = 4 min (I would do it by making a few guesses and interpolating)

at the top is easy because then you know that h = 10 and r = 6

- Calculus -
**Tim**, Saturday, December 17, 2011 at 6:13pmOK, I understand now. Thanks for all of your help.

- Calculus -
**Tim**, Sunday, December 18, 2011 at 4:06pmIn the 2nd question (rate of water rising now), how do you calculate r?

**Answer this Question**

**Related Questions**

Calculus - A cup has a radius of 2" at the bottom and 6" on the top. It is 10" ...

calculus ( related rates ) - a paper cup in the shape of a cone has a diameter ...

Calculus(answer needed immediatly,thanks) - A paper cup has the shape of a cone...

Calculus - A water trough is 6 m long, and its cross-section has the shape of an...

calculus - water is poured into a conical paper cup so that the height increases...

8th grade - Dimensions of a paper cup. The volume of a paper cup, shaped like a ...

Physics - 7. A plastic cup, 15.0 cm in height, is filled to the rim with water. ...

science - A test liquid has a density of 1.1 g/ml. When you pour some of it into...

fish tank;; deals with volume. :] - A cylinder shaped fish talk is 40cm high ...

calculus - Water is pouring into a conical vessel 15cm deep and having a radius ...