What is air resistance?

Air resistance is a force that acts in opposition to the movement of an object as it travels through the air. This force is commonly encountered by moving objects, such as cars, airplanes, or even a falling object like a skydiver. When an object moves through the air, it collides with air molecules, which creates a drag force that slows the object down. This phenomenon is especially significant at high speeds or when the object has a large surface area. Understanding air resistance is essential in physics because it illustrates how forces interact with motion and highlights the factors that affect an object's velocity and acceleration in the presence of opposing forces.

The other options do not accurately define air resistance. It is not a force that boosts speed or a type of friction that occurs on the ground, nor is it a gravitational force, which works differently by pulling objects towards the center of the Earth. Instead, air resistance is an important factor in analyzing forces acting on objects in motion through the atmosphere.