Answer:
The speed will be "3.58 ft/s". The further explanation is given below.
Explanation:
Number of knots
= 15
For the similarity of Froude number:
⇒  [tex]\frac{V_{m}}{\sqrt{g_{m}l_{m}} }=\frac{V}{\sqrt{gl} }[/tex]
Here,
[tex]l = length[/tex]
[tex]g_{m}=g[/tex]
⇒  [tex]\frac{V_{m}}{V}=\sqrt{\frac{l_{m}}{l} }[/tex]
  [tex]V_{m}=\sqrt{\frac{1}{50} }\times number \ of \ knots[/tex]
     [tex]=\sqrt{\frac{1}{50}}\times 15[/tex]
     [tex]=2.12 \ knots[/tex]
Now,
⇒  [tex]1 \ knots=0.514\times 3.281[/tex]
         [tex]=1.69 \ ft/s[/tex]
So that,
⇒  [tex]V_{m}=2.12\times 1.69[/tex]
     [tex]=3.58 \ ft/s[/tex]
