Question

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?

Answer 1

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

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

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

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