A body is projected horizontally with a velocity of 4 2 ~m / sec ....

After $0.7 \mathrm{sec}$ the horizontal velocity component of the body $=4 \sqrt{2} \mathrm{~m} / \mathrm{sec}$ since there is no change in velocity in horizontal direction. The vertical velocity component after 0.7 seconds $=0+g t=0+0.7 \times 10$ $=7 \mathrm{~m} / \mathrm{sec}$ $\therefore$ Resultant velocity of the body $=\sqrt{(4 \sqrt{2})^2+7^2}$ $=\sqrt{32+49}=9 \mathrm{~m} / \mathrm{sec}$