Answer:
vi = 5.25 m/s
Explanation:
We can determine the initial velocity of the runner by using the first equation of motion, as follows:
[tex]v_f = v_i + at\\[/tex]
where,
vf = final speed of the runner = 4 m/s
vi = initial speed of the runner = ?
a = deceleration of the runner = - 0.25 m/s²
t = time taken = 5 s
Therefore,
[tex]4\ m/s = v_i + (-0.25\ m/s^2)(5\ s)\\v_i = 4\ m/s + 1.25\ m/s\\[/tex]
vi = 5.25 m/s
