Final answer:
Air resistance is a form of frictional force that slows down the motion of objects as they travel through the air.
Step-by-step explanation:
In the subject of physics, air resistance is a form of frictional force that slows down the motion of objects as they travel through the air. It is caused by the interaction between the moving object and the molecules in the air.
For example, when an object falls through the air, air resistance acts in the opposite direction of its motion, causing it to fall slower than it would in a vacuum. Similarly, when a car moves forward, it pushes the air in its direction of motion, which creates air resistance that opposes the car's movement.