CBSE Class 9 Answered

Basically, it is friction between an object and the air.All matter is made from atoms and/or molecules. The air is no exception. When something moves through the air, it bumps into the atoms and molecules.Even though atoms and molecules are very tiny and very light, each collision causes a force on the moving object (the car) The force from each individual collision is therefore very tiny. There are however millions of these collisions each second so millions of tiny forces add up to make a large overall force.It is this big force that is called air resistance.

In case of the parachute,the air resistance counter acts the weight and the acceleration of falling down reduces considerably ,enabling the diver to land smoothly.