Define free fall.

Free fall is the motion of an object under the influence of gravity alone.

When an object is in free fall, it is accelerating at a constant rate of 9.81 m/s^2 towards the ground. This acceleration is due to the force of gravity acting on the object. The acceleration of free fall is denoted by the symbol g and is a constant value on Earth.

The motion of an object in free fall can be described using the equations of motion. For example, the distance fallen by an object in free fall can be calculated using the equation:

d = 1/2gt^2

where d is the distance fallen, g is the acceleration due to gravity, and t is the time taken for the object to fall.

The velocity of an object in free fall can also be calculated using the equation:

v = gt

where v is the velocity of the object and t is the time taken for the object to fall.

It is important to note that air resistance can affect the motion of an object in free fall. In the absence of air resistance, all objects in free fall will experience the same acceleration due to gravity, regardless of their mass or size. This is known as the equivalence principle and was famously demonstrated by Galileo in the 16th century.