Question

Which of the following gives the magnitude of the average velocity (over the entire run) of an athlete running on a circular track with a circumference of 0.5 km, if that athlete runs a total length of 1.0 km in a time interval of 4 minutes?
a. O m/s
b. 2 m/s
c. 4.2 m/s
d. 16.8 m/s

Answer 1

Answer:

c. 4.2 m/s

Explanation:

The definition of the average velocity, measured in meters per second, is given by the following expression:

$\bar v = \frac{x_{f}-x_{o}}{t_{f}-t_{o}}$

Where:

$x_{o}$, $x_{f}$ - Initial and final positions, measured in meters.

$t_{o}$, $t_{f}$ - Initial and final instants, measured in seconds.

Positions and instants must be written in meters and seconds, respectively:

$x_{o} = 0\,m$, $x_{f} = 1000\,m$.

$t_{o} = 0\,s$, $t_{f} = 240\,s$.

Finally, the average velocity of the athlete that runs a total length of 1.0 kilometer in a time interval of 4 minutes is:

$\bar v = \frac{1000\,m-0\,m}{240\,s-0\,s}$

$\bar v = 4.167\,\frac{m}{s}$

Hence, the best option is C.