The shapes of cars and planes are streamlined. Why?

Explanation

When a body moves through a fluid, its motion is opposed by the force of fluid friction, which increases with the speed of the body. When cars and planes, move through air their motion is opposed by the air friction, which in turn, depend upon the shape of the body . it is due to this reason that the cars or planes are given such shapes (known as stream-lined shaped) so that air friction is minimum. Rather the movement of air layer on the upper and lower side of streamlined shaped body provides a lift which helps in reducing the solid friction, resulting in rncreasing the speed of the car.