How to reduce frictional force?
The formula for the friction force is Ftr = M * N, where M is the coefficient of friction, N is the reaction force of the support.
In simple cases, when the body moves in a straight line, N = mg, where m is the mass of the body, g is the acceleration of gravity, for the Earth the value is constant.
Thus, Ftr = M * N = Mmg, hence the friction force depends on the mass and the coefficient of friction, and the dependence is straight.
If the body is not a system of bodies, and it cannot be unloaded, then it remains to manipulate the coefficient.
To reduce surface roughness, you can use lubricants, grinding, streamlined bodies.
Because the rolling friction force is less than the sliding friction force, it is possible to replace one type with another. For example, use bearings in mechanisms.
