What is a "hollow cylinder"

Hollow Cylinder
Rotating a rectangle with no sides touching the axis of rotation forms the hollow cylinder.

Volume Formula:
V=π(r1)^2h- π(r2)^2h

Surface Area Formula:
SA=2π(r1)^2-2π(r2)^2+2 π(r1)h+2 π(r2)h

Relationship between the volume and surface area when a particular plane figure is rotated around two different axes of rotation such as the x-axis and y-axis:

When you rotate rectangle EFGH around the x-axis, you get a hollow cylinder. The radius of the outer cylinder (r1) is 5 and the height is 4. The radius of the inner cylinder (r2) is 2 and the height is 4.

When you rotate rectangle EFGH around the y-axis, you get a cylinder. The radius is 4 and the height is 3.

There is no relationship between the volume and surface area when a particular plane figure is rotated around two different axes of rotation such as the x-axis and y-axis.