Question

An athlete completes one round of a circular track of radius 7 m in 10 s find his avg speed and average velocity

Answer 1

$$\begin{gathered} \mathrm{Average}\mathrm{speed}: \\ \mathrm{v}=\frac{\mathrm{total}\mathrm{distance}}{\mathrm{total}\mathrm{time}} \\ =\frac{2\mathrm{\pi r}}{\mathrm{t}} \\ =\frac{2\mathrm{\pi }\times 7}{10} \\ \mathbf{}\mathbf{}\mathbf{}\mathbf{=}\mathbf{4}\mathbf{.}\mathbf{4}\mathbf{}\mathbf{m}\mathbf{/}\mathbf{s} \\ \mathrm{Average}\mathrm{velocity}: \\ \mathrm{v}=\frac{\mathrm{total}\mathrm{displacement}}{\mathrm{total}\mathrm{time}} \\ \mathrm{After}\mathrm{completing}\mathrm{one}\mathrm{round},\mathrm{starting}\mathrm{and}\mathrm{ending}\mathrm{points}\mathrm{are}\mathrm{same}. \\ \mathrm{Hence},\mathrm{the}\mathrm{total}\mathrm{displacement}\mathrm{is}\mathrm{equal}\mathrm{to}\mathrm{zero}. \\ \mathrm{So}, \\ \mathrm{v}=\frac{0}{\mathrm{t}} \\ \mathbf{}\mathbf{}\mathbf{=}\mathbf{0} \end{gathered}$$