Question

A stone is dropped from the edge of a roof.
a) how long does it take to fall 4.9m?
b) How fast does it move at the end of that fall?
c) What is its accelerations after 1s and after 2s?

Answer 1

$$\begin{gathered} DearStudent, \\ a)Here, \\ s=4.9m,u=0,a=g \\ Wehave, \\ s=ut+\frac{1}{2}a{t}^2 \\ \Rightarrow \\ 4.9=0+\frac{1}{2}\times 9.8\times t^2=4.9t^2 \\ Timetakentocover4.9mis, \\ {t}^2=\frac{4.9}{4.9}=1 \\ \Rightarrow \\ \mathit{t}\mathbf{=}\mathbf{1}\mathit{s} \\ b)Heretotaldis\tan cecoveredistakenas,s=4.9m \\ Wehave, \\ {v}^2=u^2+2as \\ \Rightarrow \\ {v}^2=0+2\times 9.8\times 4.9=9.8\times 9.8 \\ Finalvelocityis, \\ v=\sqrt{9.8\times 9.8}=\mathbf{9}\mathbf{.}\mathbf{8}\mathit{m}\mathbf{/}\mathit{s} \\ c)Theacccelerationofafreelyfaillingbodyremainsthesameatalltimes. \\ i.e,.a=\mathit{g}\mathbf{=}\mathbf{9}\mathbf{.}\mathbf{8}\mathit{m}\mathbf{/}{\mathit{s}}^{\mathbf{2}},after1sandafter2s. \\ Regards. \end{gathered}$$