A running man has half the kinetic energy of that of a boy of half of his mass. The man speeds up by 2 m/s so as to have the same kinetic energy as that of the boy. The initial speed of the man was:
1
\(\sqrt2 \,m/s\)
2
\(\sqrt2-1\,m/s\)
3
\(\frac{2}{\sqrt2-1}\,m/s\)
4
\(\frac{1}{\sqrt2}\,m/s\)