A Random Doubt

As usual my mind was roaming around lazily and foolishly. I was thinking a little about balls, circles and spheres. A circle viewed in a three dimension gives a sphere. Thats fine. A metal shotput that some of those sportspersons throw can be considered a sphere. I remember my school friend rajaram throw shot put to long distances. In National level two quick names that come up in shotput throwing are Shakti Singh and some Neelam somebody. Well a ShotPut is a full sphere. Even a golf ball or tennis ball or a billiards ball will qualify for a full sphere. To find the capacity of these kind of balls we can use the formula for volume of sphere. ( I think so) .

Well if the sphere is hollow?. Volume of hollow sphere can be used. But then what is a hollow sphere. Is football or volleyball which dont have any material inside which have only the outer shell, can they be classified a hollow sphere??.

Or is it a ring ball??. Hmm we used to play ring ball in school during evenings. we used to have cut shot ,etc, etc. The ring ball is what causing me some trouble. The ring ball has a circular covering rubber. However the ringball can not come under the category of a circle. Can it come under sphere?? Am perplexed. It just has a big hole covered by a thick circular rubber. is this a hollow sphere or is the football a hollow sphere.
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Getting the above basics right would lead me an answer to the below questions that are pegging me.

What is the formula to calculate a Volume of Golf Ball
What is the formula to calculate a Volume of Foot Ball
What is the formula to calculate a Volume of Ring Ball