9514 1404 393
Answer:
 6 feet
Explanation:
The volume of a cylinder is given by ...
 V = πr^2·h
For a sphere, the volume is ...
 V = 4/3πr^3
You want the volumes to be the same when h=8, so we have ...
 πr^2·8 = 4/3πr^3
Dividing by πr^2, we have ...
 8 = 4/3r
 r = 3/4·8 = 6
The radius is 6 feet.