Question

(1) We used
--- to reduce friction.​

Answer 1

Explanation:

By polishing the surface, as polishing makes the surface smooth and friction can be reduced. Using lubricants such as oil or grease can reduce the friction between the surfaces. When objects are rolled over the surface, the friction between the rolled object and surface can be reduced by using ball bearings.

Answer 2

Explanation:

1. polishing the rough surface

2. oiling or lubricating with graphite or grease the moving part of a machine

3. Providing all bearings or wheels between the moving parts of a machine or vehicles reduce friction and allow smooth movement as rolling friction is less than sliding friction.