Physics - Kinematics Question with Solution | TestHub

Let ' $t$ ' be the time taken by the bullet to hit the target. $$\begin{array}{rl}& \therefore 700\mathrm{m}=630{\mathrm{ms}}^{-1}t\\ & \Rightarrow t=\frac{700\mathrm{m}}{630{\mathrm{ms}}^{-1}}=\frac{10}{9}\sec \end{array}$$ For vertical motion, Here, $u=0$ $$\begin{array}{rl}& \therefore h=\frac{1}{2}g{t}^2\\ & =\frac{1}{2}\times 10\times {\left(\frac{10}{9}\right)}^2\end{array}$$ $$=\frac{500}{81}\mathrm{m}=6.1\mathrm{m}$$ Therefore, the rifle must be aimed $6.1\mathrm{m}$ above the centre of the target to hit the target.