Final answer:
A free falling object demonstrates Newton's second law of motion, where its acceleration is due to gravity acting as the net force.
Step-by-step explanation:
An object that is free falling in the air is demonstrating Newton's second law of motion. According to this law, the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. When an object falls, only gravity (ignoring air resistance) is acting on it, causing it to accelerate towards the Earth at 9.8 m/s2. This is a practical application of Newton's second law, where the acceleration (a) is due to the gravitational force (F), with the mass (m) of the object being a constant factor (a = F/m).