Question

An athlete of mass 70kg starts his race with a speed of 10m/s. During the race he suffers from some physical problem so he finishes his race with 10% of his initial kinetic energy. Find final speed of the athlete

Answer 1

$$\begin{gathered} \frac{1}{2}{{\mathrm{mv}}_1}^2=10\%\mathrm{of}\mathrm{initial}\mathrm{KE} \\ =0.1\times \frac{1}{2}{\mathrm{mv}}^2 \\ {{\mathrm{v}}_1}^2=0.1{\mathrm{v}}^2 \\ =0.1\times {10}^2 \\ {\mathrm{v}}_1=\mathbf{3}\mathbf{.}\mathbf{16}\mathbf{}\mathbf{m}\mathbf{/}\mathbf{s} \end{gathered}$$