The application of decreasing friction includes :

Friction opposes the relative motion between two surfaces in contact. Friction is sometimes undesirable.

Friction can be reduced by:

i. using ball bearings in moving parts of the machine.

ii. giving suitable shapes to bodies moving in fluids. For example, the streamlined shape of an aircraft

iii. using air cushion between the moving parts. For example, the layer of air between the hull of a hovercraft.