Friction

Friction is the resistance or opposition to slide one body over another. When we walk there is friction between the ground and the soles of our shoes. When a car runs, there is friction between the tires and the ground.

Uses of Friction
Friction is useful in many ways. If there is no friction we cannot attach things together. The nails and screws will not work and we cannot have houses. Dresses cannot be sewed. Even trees cannot stand and the roots cannot hold to the ground. Machines will not work without friction. The parts of machines will just slide and slip and nothing can be done.

Ways of Increasing Friction
Friction may be increased by scattering sand and pebbles on the road during rainy days when the road is slippery. This is especially true in cold countries where ice and snow cover the road. Chains are attached to the wheels of vehicles to increase friction. Shoes of runners (athletes) have spikes. Tires of automobiles and trucks have designs curved on them. The soles of rubber shoes have carved designs not just to make them look better but to increase friction.

Ways of Reducing Friction
Friction may be reduced by (1) the use of oil or grease (2) making the surface smooth by planning, filing, sandpapering or scrubbing as in floors (3) streamlining. Jet and airplanes nowadays have cambered wings and well-shaped bodies. Cards have rounded tops and nicely curved backs and fronts. Ships are elongated in shape. All these are done to reduce friction and enable the vessels to move faster in air or water. (4) Using ball or roller bearings. Roller skates make a good example. Many machines have ball bearings.