When we neglect air resistance in free fall problems, we assume that there is no force acting on the falling object except for gravity. In reality, air resistance or drag is a force that opposes the motion of an object moving through the air. It becomes more significant as the speed of the object increases.
When air resistance is neglected, the object is assumed to fall under the influence of gravity alone, following the laws of motion and acceleration due to gravity. This simplification allows for easier calculations and provides a theoretical model for understanding the basic principles of free fall.
Neglecting air resistance in free fall problems typically results in idealized scenarios where objects fall with constant acceleration and their motion can be described by simple kinematic equations. The object's velocity and displacement can be determined accurately based on the initial conditions and the acceleration due to gravity (9.8 m/s² near the surface of the Earth).
However, in real-world situations where air resistance is not negligible, the motion of a falling object becomes more complex. The presence of air resistance affects the object's acceleration, velocity, and trajectory. As the object gains speed, the air resistance force increases until it becomes equal to the force of gravity, resulting in a terminal velocity where the object falls at a constant speed without accelerating further.
In summary, neglecting air resistance in free fall problems simplifies the calculations and provides an idealized scenario, but it does not accurately represent the behavior of objects falling in the presence of air resistance.