Two bodies of mass 4g and 25g are moving with equal kinetic...

The kinetic energy $\left(K\right)$ of an object is given by

$\begin{cases}K & = & \dfrac{1}{2}m{v}^{2} \\ & = & \dfrac{{p}^{2}}{2m} . . . \left(1\right)\end{cases}$

Following equation (1), for the two given bodies, it can be written that

${p}_{1}^{2}2{m}_{1} = {p}_{2}^{2}2{m}_{2} ⇒ \dfrac{{p}_{1}}{{p}_{2}} = \sqrt{\dfrac{{m}_{1}}{{m}_{2}}} = \sqrt{\dfrac{4}{25}} = \dfrac{2}{5}$