Answer
A circular cylinder with radius $5$ along the z-axis.
Work Step by Step
Given: $r=5$
As we know that $r^2=x^2+y^2 \implies r=\sqrt{x^2+y^2}$
Thus, we have
$\sqrt{x^2+y^2}=5$
This can be written as:
$x^2+y^2=5^2$
Thus, it represents an equation of a circular cylinder with radius $5$ along the z-axis.
