Physics

Problem

A runner travels on a straight road. For the first

20\,\text{s}

the runner's velocity is

+4.0\,\text{m/s}

. For the next

10\,\text{s}

the velocity is

-6.0\,\text{m/s}

. Positive direction is north. Which of the following pairs gives the runner's average velocity and average speed for the entire

30\,\text{s}

interval? a)

+4.7\,\text{m/s}

;

4.7\,\text{m/s}

-0.67\,\text{m/s}

;

4.7\,\text{m/s}

+0.67\,\text{m/s}

;

4.7\,\text{m/s}

+0.67\,\text{m/s}

;

5.0\,\text{m/s}