Final answer:
True, the net force on a person sitting still in a chair is zero because the gravitational force is balanced by the normal reaction force from the chair, leading to a state of equilibrium.
Step-by-step explanation:
The statement that the net force acting on you when you sit still in a chair is zero is True. When you're sitting still, there's a force due to gravity pulling you down, which is your weight. This is balanced by an equal and opposite force known as the normal reaction force, which is the chair pushing up against you. Both forces are acting on you in opposite directions and have equal magnitudes, so they cancel each other out, resulting in a net force of zero. This is an example of what's known in physics as a state of equilibrium, where all forces are balanced and there is no acceleration. In other words, the force of gravity is canceled out by the normal force, leading to a net force of zero. This is why you don't fall through the chair.