Answer
$3.25\frac{m}{s}$
Work Step by Step
We know that
$p=\frac{h}{\lambda}$
$p=\frac{6.63\times 10^{-34}}{122\times 10^{-9}}$
$p=5.43\times 10^{-27}Kg.\frac{m}{s}$
As $p=m_hv$
We plug in the known values to obtain:
$5.43\times 10^{-27}=1.67\times 10^{-27}v$
$\implies v=3.25\frac{m}{s}$
