Question

what are the 20 objects produces and reduce friction

Answer 1

There are following name of materials which reduce friction.
1. water
2.Plane Surfaces
3.Grace
4.Movle
5.Round or circular Ball
6.Poweder
7.Oil
8.kerosene
etc........

Now there are following name of material which produce friction.

1.Sand
2.rubber materials
3.Rough Surfaces
etc...............

Answer 2

Friction is reduced by adopting the following methods -

By polishing the suffaces
By applying oil or grease on the surfaces ( or by lubrication)
By sprinkling a soft, slippery fine powder on the surfaces as we do on our carrom board.By using wheels, ball-bearings or roller-bearings in machines.By streamlining the body of an object like those of aeroplanes, rockets, ships, etc. Birds and fish also have streamlined bodies.