The egg drop experiment is a staple in most physics classes. It is used to demonstrate basic, yet fundamental, concepts in physics, the forces applied to a falling object. The main concepts covered by this experiment are: gravity, free fall, air resistance and terminal velocity.

### Gravity

Gravity is a common concept that is most closely defined as a force that exists between the Earth and objects near it. There are two key concepts when defining gravity. The first is the force of gravity (represented by Fgrav); this is the force that acts upon objects on or near the Earth’s surface. The force of gravity can be calculated by the equation Fgrav = mass * acceleration. Then there is the acceleration of gravity (represented as g). The acceleration of gravity is the acceleration experienced by an object when gravity is the only force applied to the object. All objects on or near the Earth’s surface have the same value for the acceleration of gravity (g), 9.8 m/s/s (meters per second per second).

### Free Fall

A free falling object is one that is falling under the sole influence of the force of gravity. There are two characteristics that will define an object in free fall; the first is that the object does not encounter air resistance, and the second is that all free falling objects fall to the Earth at a rate of 9.8 m/s/s.

### Air Resistance

Air resistance occurs when the leading surface of a falling object collides with air molecules. There are two most common factors that can change air resistance: the speed of the object and the cross-sectional area of the object. An increase in speed will increase air resistance; also an increase in the area of an object will increase air resistance. When an object in free fall encounters air resistance, the equation is then Fnet = mass * acceleration, where Fnet is the difference between the force of gravity and the force of the air resistance.

### Terminal Velocity

Terminal velocity is defined as the steady speed of an object freely falling through a gas or a liquid. As an object falls and encounters an increase in air resistance, eventually the air resistance will balance the force of gravity and this concept is terminal velocity. Therefore, the force of air resistance is proportional to the speed of the object so that air resistance will increase as the speed of the object increases until terminal velocity is reached.