Final answer:
In physics, the term 'fall' refers to the motion of an object under gravity's influence, encompassing both descent and ascent. Free fall specifically describes this motion under gravitational force alone. The concept is used to understand the forces at play in theme park rides and other motion problems.
Step-by-step explanation:
The term fall used in the sentence, "As the car leaves the lift hill, the train begins to fall down the track," refers to the motion of the roller coaster train under the influence of gravity. This is an example of free fall, wherein the only force acting on an object is the gravitational force. Though the term 'fall' typically suggests a movement from higher to lower ground, in physics, it encompasses both the downward movement after an object is dropped, as well as the upward path when an object is thrown up before it starts its descent again due to gravity.
Free fall and the concepts applied, such as the constant acceleration due to gravity, are critical to understanding various motion problems. In discussing amusement park rides, like the vertical barrel ride, it is essential to distinguish between perceived fictitious forces and actual forces like gravity and the normal force. When analyzing the barrel ride in an inertial frame of reference, riders are pinned to the wall not by a fictitious force, but by the centrifugal force due to the rotation of the barrel, while the real force acting is the centripetal force directed towards the center of the rotation.