To find the final velocity of the runner, we can use the equation that relates displacement, initial velocity, final velocity, and acceleration during uniform acceleration:
d = (1/2) * (v_f + v_i) * t
Where: d is the displacement (12m in this case), v_f is the final velocity (the value we want to find), v_i is the initial velocity (which is 0 since the runner starts from rest), t is the time interval (2s in this case).
Plugging in the given values into the equation, we have:
12 = (1/2) * (v_f + 0) * 2
Simplifying:
12 = v_f * 1
12 = v_f
Therefore, the final velocity of the runner is 12 m/s.