Final answer:
The statement that an object in free fall accelerates due to Earth's gravity is true. Free falling objects are subjected to a constant acceleration due to gravity which is 9.80 m/s² when air resistance is negligible. The real-world scenario includes air resistance, which prevents true free fall.
Step-by-step explanation:
When an object is in free fall, the only force acting upon it is the force of gravity. This statement is true. Objects in free fall experience a constant acceleration when air resistance is negligible. On Earth, this acceleration due to gravity, represented as 'g', averages 9.80 m/s². In the context of Newton's Third Law of Motion, when a person walks on the ground, they exert force on the ground (F1), and the ground exerts an equal but opposite force (F2) on the person. However, the person is able to walk because these two forces act on different systems, and the net force acting on the person is nonzero, allowing for acceleration and movement.
While the theory of free fall assumes a vacuum where no air resistance exists, in the real world, air resistance always applies some upward force on falling objects. Hence, objects on Earth do not experience true free fall, but the concept applies for educational and theoretical discussions about gravity and motion.