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A runner circles the track exactly 2 times for distance of 800m. it takes 4.0min. what is her average speed in m/s? what is her average velocity?

1 Answer

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If the runner ends where she started, then her total displacement is
\Delta x=0\,\mathrm m, which means her average velocity will be


\bar v=(\Delta x)/(\Delta t)=\frac{0\,\mathrm m}{4.0\,\mathrm{min}\cdot\frac{60\,\mathrm s}{1\,\mathrm{min}}=0\,(\mathrm m)/(\mathrm s)

The total distance she traversed, however, was
\Delta d=800\,\mathrm m, which gives her an average speed of


\bar s=(\Delta d)/(\Delta t)=\frac{800\,\mathrm m}{4.0\,\mathrm{min}\cdot\frac{60\,\mathrm s}{1\,\mathrm{min}}=3.3\,(\mathrm m)/(\mathrm s)

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