Answer:
[tex]v=3.5\frac{m}{s}[/tex]
Explanation:
The average speed is defined as:
[tex]v=\frac{\Delta x}{\Delta t}[/tex]
Using the equations for uniformly accelerated motion, we calculate the runner's acceleration:
[tex]a=\frac{v_f-v_o}{2}\\a=\frac{7\frac{m}{s}-0\frac{m}{s}}{2s}\\a=3.5\frac{m}{s^2}[/tex]
Now, we can calculate the distance that the runner travels:
[tex]\Delta x=v_0t+\frac{at^2}{2}\\\Delta x=(0\frac{m}{s})(2s)+\frac{3.5\frac{m}{s}(2s)^2}{2}\\\Delta x=7m[/tex]
Finally, we calculate the runner's average speed:
[tex]v=\frac{7m}{2s}\\v=3.5\frac{m}{s}[/tex]
