A vessel containing liquid of density  ${\rho }_0$ is accelerated horizontally with constant acceleration $12\text{ m}/{\text{s}}^2$  in gravity free space. A small sphere of density  $2{\rho }_0$  is released from rest with respect to the vessel. Magnitude of initial horizontal acceleration of sphere with respect to vessel is……………… $\text{m}/{\text{s}}^2$