# Drinking glass

talzamir
Posers and Puzzles 27 Oct '11 23:45
1. talzamir
Art, not a Toil
27 Oct '11 23:45
A drinking glass has a round base with radius r1, height of h and radius r2 > r1 at the upper rim. On its side on the table the glass goes around in a circle. How many full rotations does the glass do during one such circle?
2. 28 Oct '11 04:551 edit
I get {[h^2 + (r2-r1)^2]^(1/2)}/(r2-r1).
3. joe shmo
Strange Egg
28 Oct '11 05:031 edit
Originally posted by talzamir
A drinking glass has a round base with radius r1, height of h and radius r2 > r1 at the upper rim. On its side on the table the glass goes around in a circle. How many full rotations does the glass do during one such circle?
I'll say

Theta = 2*pi*(r2-r1)/h

Theta = 2*pi

so number of rotations is

N = (r2-r1)/h
4. 28 Oct '11 05:37
Originally posted by joe shmo
I'll say

Theta = 2*pi*(r2-r1)/h

Theta = 2*pi

so number of rotations is

N = (r2-r1)/h
I do not think your answer will yield the right trends with respect to parameter variations. For example, consider if (r2-r1) becomes very small (for some constant h). N should get very big because the glass will sweep out a very large circle, right?
5. joe shmo
Strange Egg
28 Oct '11 05:50
Originally posted by LemonJello
I do not think your answer will yield the right trends with respect to parameter variations. For example, consider if (r2-r1) becomes very small (for some constant h). N should get very big because the glass will sweep out a very large circle, right?
yeah...I suppose so. I did it hastily while I'm slightly under the influence...sorry