A drop tower is a terrifying amusement park ride in which you are strapped into a seat, lifted high in the air, and then dropped. While you're in free fall, what is your apparent weight?

When discussing amusement park rides like a drop tower, we must first understand the concept of gravitational force. Gravitational force is the pulling force that Earth exerts on objects, bringing them towards its center. It is calculated using the formula: \[ F = m \times g \] where \( F \) is the gravitational force, \( m \) is the mass of the object, and \( g \) is the acceleration due to gravity. For Earth, \( g \) is approximately 9.8 m/s². Every object with mass is pulled by this force. Your real weight, often called true weight, is actually this gravitational pull. You feel this force constantly as you stand or move on the Earth’s surface.

Free fall is a state in which an object is only acted upon by the force of gravity, with no other forces providing resistance. For instance, when you are dropped from a height on a drop tower ride, you experience free fall. During free fall, the object accelerates at a rate equal to the acceleration due to gravity (9.8 m/s²), assuming air resistance is negligible. This acceleration causes you to feel weightless, as there are no other forces (like the normal force) acting upon you. Free fall creates a unique sensation because, in everyday life, we always experience a normal force from the ground or objects we interact with, counteracting gravitational pull. Without this normal force, such as in free fall, you momentarily experience a state of apparent weightlessness.

Normal force is the force exerted by a surface to support the weight of an object resting on it. It acts perpendicular to the surface. If you’re standing on the ground, the ground provides an upward normal force that balances the downward gravitational force. This normal force is what we often interpret as our apparent weight. In the context of a drop tower ride, once you’re released and are in free fall, there is no surface providing an upward force. As a result, the normal force is zero. Here’s how this looks mathematically: During free fall: \[ N = 0 \] where \( N \) represents the normal force. Because apparent weight is defined by the normal force, your apparent weight becomes zero during free fall.

Whenever objects fall towards Earth, they do so because of the acceleration due to gravity, denoted as \( g \). This constant is approximately 9.8 m/s² and it characterizes how quickly something speeds up as it falls. When in free fall, an object’s velocity increases by 9.8 meters per second every second it’s falling, provided that air resistance is negligible. This acceleration is the reason why, even though weights may differ, all objects fall at the same rate in a vacuum. Understanding this concept is crucial for analyzing scenarios like free fall in amusement park rides. The acceleration due to gravity is the driving force behind the sensation of weightlessness experienced during these drops.