Question

A runner starts from rest and in 2 s reaches a speed of 7 m/s. If we assume that the speed changed at a constant rate (constant net force), what was the average speed during this 2 s interval.

Answer 1

`v=3.5(m)/(s)`

Step-by-step explanation:

The average speed is defined as:

`v=(\Delta x)/(\Delta t)`

Using the equations for uniformly accelerated motion, we calculate the runner's acceleration:

`a=(v_f-v_o)/(2)\\a=(7(m)/(s)-0(m)/(s))/(2s)\\a=3.5(m)/(s^2)`

Now, we can calculate the distance that the runner travels:

`\Delta x=v_0t+(at^2)/(2)\\\Delta x=(0(m)/(s))(2s)+(3.5(m)/(s)(2s)^2)/(2)\\\Delta x=7m`

Finally, we calculate the runner's average speed:

`v=(7m)/(2s)\\v=3.5(m)/(s)`