Question

How far to the nearest tenth of a meter can a runner running at 10 m/s run in the time it takes a rock to fall from rest 91 meters

Answer 1

Use kinematics to find the time it will take the rock to fall to the ground.

(delta)x = V(initial)(time) + .5at^2

(delta)x = 0 + .5(-9.8)t^2

First term drops out because initial velocity is zero.
Acceleration is that due to gravity.
Negative sign is because it is accelerating downward, so technically the (delta)x will be negative as well so that you will not be square rooting a negative number.
You should be able to get it from here.

Answer 2

20.5