what is air drag ?
Air drag basically means the resistance offered by air to the flow of any body through it. So, air tends to slow down any body travelling through it.
For example. when we throw a ball horizontally it gradually slows down and falls to the ground due to gravity and air resistance.
Similarly, like air, all mediums exert resistive forces to any body flowing through them.
In fluid dynamics, drag refers to forces which act on a solid object in the direction of the relative fluid flow vilocity. Unlike other resistive forces, such as dry friction, which is nearly independent of velocity, drag forces depend on velocity.Drag forces always decrease fluid velocity relative to the solid object in the fluid's path.