A unit speed is obtained by which of the following equations with usual notations?
1
\({N_u} = \frac{N}{{\sqrt H }}\)
2
\({N_u} = \frac{{\sqrt N }}{H}\)
3
\({N_u} = \frac{{\sqrt N }}{{\sqrt H }}\)
4
\({N_u} = \frac{{{N^{\frac{2}{3}}}}}{{{H^{\frac{1}{5}}}}}\)