Here is a problem I have been developing. Maybe somebody can
tell me if it can be solved or if more information is needed.
Three solid balls of radii a, b, and c are placed in a bowl
whose inner surface is a hemisphere of radius d.
The following information is known:
1) a < b < c < d,
2) d is large enough so that each ball touches a point on
the inner surface of the bowl,
3) a is large enough so that each ball touches the other
4) the balls are made of the same material so that their
weights are proportional to their volumes,
5) the forces that the balls exert on each other and the
bowl are directed along the lines determined by their
After the balls come to rest, what is the angle between
the plane determined by the centers of the balls and the
horizontal in terms of a, b, c, and d ?
(In reply to Some thoughts and a question
Is this identical to the balls hanging from strings (length d minus ball diameter) that are anchored at a common point?
Mighty nice way of transforming the problem, great thinking.
It would change the difficulty setting by one or two categories I guess.
I am not absolutely sure, it is difficult to visualise it , but I believe that it is unfortunately not identical.
As to the problem:
I guess all the necessary information is available to solve the problem.
This said, I don't see myself solving it (certainly not in a reasonable time), but I am very interested in the method used/progress made in solving it.
I would first calculate the function that expresses the coordinates of the center of gravity of the 3 balls in terms of a, b, c and d
Then I would evaluate this function for the center of c going from height c to height say 2c. The minimum value of this function would give you an answer where c must be.
a and b coordinates can probably be calculated relatively easy, then the plane, then the angle.
Posted by Hugo
on 2005-09-07 21:12:46