How to reduce friction
This will depend on the surface that is experiencing friction. However, in most substances, friction is reduced by the use of a lubricant like grease. Friction can also be reduced through the use of materials that can't be affected by the friction. Get more tips on http://www.machinerylubrication.com/Read/29181/reduce-friction-surfaces and http://www.ehow.com/how-does_5032819_ball-bearings-reduce-friction.html.
lubrication,same as an engine.