Laws Of Motion

A block of mass 5 kg is kept on a smooth horizontal surface. A horizontal stream of water coming out of a pipe of area of cross-section $5 \mathrm{~cm}^{2}$ hits the block with a velocity of $5 \mathrm{~ms}^{-1}$ and rebounds back with the same velocity. The initial acceleration of the block is (density of water is $1 \mathrm{~g} / \mathrm{cc}$ )