Answer:
\boxed{\text{8 ft}}
Step-by-step explanation:
The formula for the volume of a cube is
V = s³
where s is the length of a side.
[tex]\begin{array}{rcl}\\V&=&s^{3}\\\text{512 ft}^{3}& =&s^{3}\\\sqrt[3]{ \text{512 ft}^{3}} & = & s\\s & = & \textbf{8 ft}\\\end{array}\\\text{The length of one side is $\boxed{\textbf{8 ft}}$}[/tex]