Answer
The average force exerted is 16 N.
Work Step by Step
To find, the average force exerted, we first need to find the acceleration:
$a = \frac{v^2-v_0^2}{2x}$
$a = \frac{(13 ~m/s)^2}{(2)(2.8 ~m)}$
$a = 30.18~m/s^2$
Next, we substitute the value of $a$ in the formula and solve:
$F = ma$
$F = (7.0 ~kg)(30.18 ~m/s^2)$
$F = 211.25 ~N$
$F \approx 211.25 ~N$
The average force exerted is 211.25 N.