SOLUTION: Find the volume of a one-base paraboloid having on its base a circumference of 16π cm and an altitude of 10 cm.

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Question 587934: Find the volume of a one-base paraboloid having on its base a circumference of 16π cm and an altitude of 10 cm.
Answer by KMST(5396) About Me  (Show Source):
You can put this solution on YOUR website!
I'm not sure my solution is what your calculus teacher expects, but hopefully it will help.
I like to visualize that paraboloid in x-y-z coordinates (in cm) as the space between
z=10 and z=k%28x%5E2%2By%5E2%29 (I'll find the right k later).
The vertex of that paraboloid is at (0,0,0), with z=0.
At z=10 we have the base of the paraboloid, which is a circle.
Its radius, R is such that 2%2Api%2AR=16pi --> R=8
If we were allowed, I would search for volume, V, of a paraboloid with height h and base radius a, and find the formula
V=%281%2F2%29pi%2Aa%5E2h and for your paraboloid V=%281%2F2%29pi%2A8%5E2%2A10=320pi
In some calculus class, I would have some formula for volume of revolution solids, but I d not have it. (My 1973 Tom Apostol Calculus book has accumulated too much dust, and is probably too heavy and abstract to be of use).
So I figure out the radius, r, of a cross section as a function of z.
At z=10 , z=k%28x%5E2%2By%5E2%29=kr%5E2 is 10=k8%5E2 --> k=10%2F8%5E2
Now I have z=%2810%2F8%5E2%29r%5E2 --> r%5E2=%288%5E2%2F10%29z
Then, the area of a cross section circle is pi%2Ar%5E2=pi%2A%288%5E2%2F10%29z .
Now I'm ready to find the volume as