Hey there :)
Lets solve your question,
Given:
Speed = 56 ft/s
To find- Relative Pressure
Solution-
We know that,
[tex]V =8 \sqrt{p} [/tex]
[tex] = > p = \frac{ {v}^{2} }{64} [/tex]
[tex] = > \frac{ {(56)}^{2} }{64} [/tex]
[tex] = > 49psi[/tex]
Therefore, the answer is 49 psi