How does air resistance affect moving objects?

Air resistance, also known as drag, acts on moving objects by opposing their motion. When an object moves through the air, it collides with air molecules, which exert a force in the opposite direction of the object's velocity. This opposing force reduces the object's speed and can affect its trajectory. For example, when a car drives down the road or a skydiver falls through the atmosphere, air resistance slows them down compared to their speed in a vacuum where there is no air.

This concept is crucial in understanding how various factors can influence the motion of objects in a real-world environment, where air resistance is always a consideration. It is important to note that air resistance affects all moving objects, not just large ones, and it does not increase the speed of an object or have no effect on motion, which distinguishes it from the other choices.