Question

How can you reduce the drag on something moving on:

(a) air

(b)water

Answer 1

Those substances which are able to flow easily are called Fluids. Water and air are the most common fluids.
There is a friction whenever an object moves through a fluid.It is called fluid friction.

The frictional force exerted by a fluid is called drag.

The magnitude of frictional force or drag exerted by a fluid on an object moving through it depends on
1) speed of the object
2)shape of the object
3)size of the object
4)nature of the fluid or viscosity of the fluid



so to reduce drag in both air and water
Make it more streamlined,

Reduce its speed (very effective)’

Reduce it’s cross-sectional area,

Add boundary layer blowing,

Suck the boundary layer

Coat it with a low friction layer (Teflon, wax).

Go to higher, less dense air or water
Go to hotter air or water



please note that for both air and water the above mentioned conditions are aplicable