Final answer:
The runner, starting from rest and accelerating at 4.2 m/s² for 10 seconds, covers a distance of 210 meters.
Step-by-step explanation:
When a runner accelerates from rest, their displacement can be calculated using the kinematic equation s = ut + (1/2)at², where s is the displacement, u is the initial velocity, t is the time, and a is the acceleration. In this case, the runner starts from rest so u = 0 m/s, accelerates at a = 4.2 m/s² for t = 10 s. Plugging these values into the equation gives us the displacement: s = 0 + (1/2)(4.2 m/s²)(10 s)² = 210 m.
Therefore, the runner covered a distance of 210 meters during the 10-second time frame.