Final answer:
A person running 6 miles per hour on a level surface is in a state of dynamic equilibrium because they are moving with a constant velocity and no acceleration, indicating balanced forces.
Step-by-step explanation:
In the scenario where a person is running 6 miles per hour on a level surface, they are in a state of dynamic equilibrium. This is because dynamic equilibrium refers to the condition where a body is moving with constant velocity without acceleration in a straight line; hence, the forces on the body are balanced. In this case, even though the person is in motion, the velocity is uniform and there is no net acceleration, indicating a state of equilibrium that is dynamic rather than static.